This is a petition for review on certiorari of the decision dated March 26, 1984 of the Intermediate Appellate Court in AC-G.R. No. CV-64708 which (1) annulled the sale made by Manuela Buenavista of her property in favor of the spouses Raquel Chavez and Gerardo Gimenez (Exh. 2) and the subsequent sale by said spouses of the same property to Pepito Ferrer, and (2) declared that the earlier deeds of sale (Exhs. A, B, C and D) signed by Manuela and her children constituted a valid partition of the land, subject to her lifetime usufruct.  The Court of Appeals thereby reversed the decision dated December 21, 1971 of the Court of First Instance of Camarines Norte, Branch 1.

The land in question is the paraphernal property of petitioner Manuela Buenavista (defendant in Civil Case No. 1934 of the Court of First Instance of Camarines Norte) who had six (6) children, named Antonio, Rosario, Concepcion, Raquel, Presentacion and Floserpina.  The first three were the plaintiffs and the last three, with their mother, were the defendants in Civil Case No. 1934.

On July 11, 1958, Presentacion Chavez, with the conformity of her mother, Manuela Buenavista, executed a deed of sale whereby she sold her 1/6 undivided share of the land in question to her sister, Concepcion Chavez, for P450.

Two years later, on May 2, 1960, Floserpina Chavez, with the conformity of her mother, also sold her 1/6 undivided share of the same land to her sister, Concepcion, for the same price of P450.  On May 19, 1960, Raquel, with the conformity of her mother, likewise sold her undivided 1/6 share of the same property to Concepcion Chavez for P600.  Having acquired the shares of Presentacion, Floserpina and Raquel, Concepcion thereby became the owner of a total undivided 4/6 share of the land in question with Antonio and Rosario as owners of the remaining 2/6 shares.

In all the documents, the following stipulation appears:

"Na ang nasabing lupa o pag?aari ay ipinamana na sa amin ng aming ina, ang nasabing Manuela Buenavista, kung kaya ito ay hatiin naming anim (6) na mga magkakapatid, bagama't hindi pa namin naisasagawa ang paghihiwatig or particion; ako bilang isa sa anim na magkakapatid ay may karapatan sa isang ikaanim (1/6) na bahagi ng nasabing lupa, gayon pa man ang kasunduan sa nasabing pagkamana namin ay samanta­lang nabubuhay pa ang aming ina, siya ang magkakandili at makikinabang sa nasabing pag-aari." (p. 14, Rollo.)

meaning that the owner, Manuela Buenavista, had assigned or distributed to her children, in equal pro-indiviso shares, her paraphernal property situated at Sitio Langas, Barrio Calangcawan Norte, Vinzons, Camarines Norte, with an area of 4.1163 hectares more or less under Tax Declaration No. 9303 and assessed at P1,630.00.  The owner, however, reserved for herself the possession of the land and the enjoyment of the fruits during her lifetime.

Despite the transfers or assignments her children had executed with her conformity ten years earlier, Manuela Buenavista, on August 27, 1968, signed a "Bilihang Patuluyan ng Lupa" of the entire property in favor of her daughter, Raquel Chavez, and her husband, Gerardo Jimenez.  On October 7, 1968, Antonio, Rosario and Concepcion filed Civil Case No. 1934 against their mother Manuela and their sister Raquel.  Thereupon, Manuela sold the entire property to Pepito Ferrer, on February 4, 1969 (Exh. F) with right to repurchase.  Ferrer was later sued as an additional defendant in Civil Case No. 1934.

After the trial, judgment was rendered by the trial court dismissing the complaint, dissolving the preliminary injunction it had previously issued, and ordering the plaintiffs to pay the costs.  The court did not award damages.

The plaintiffs, Antonio, Rosario and Concepcion, appealed to the Court of Appeals (CA-G.R. No. 64708-R).

On March 26, 1984, the Court of Appeals reversed the trial court.  The dispositive portion of its decision reads:

"WHEREFORE, we reverse and set aside the appealed decision and render another one declaring the deeds of sale in favor of Raquel Chavez and Gerardo Jimenez (Exh. 2) and the sale in favor of defendant-appellee Pepito Ferrer as null and void ab initio, and declaring further that the documents (Exhs. A, B, C and D) are evidence of a valid partition of the land in question by and between Manuela Buenavista and her children, subject to her right of usufruct during her lifetime, without pronouncement as to damages and costs." (p. 17, Rollo.)

On April 5, 1984, the petitioners filed a motion for reconsideration alleging among others:

"3. That the late Manuela Buenavista Vda. de Chavez, one of the defendants-appellees, was found lately to have executed during her lifetime a LAST WILL AND TESTAMENT x x x and there is now a pending petition for probate of said last will and testament before the Municipal Trial Court of Vinzons, Camarines Norte;

"xxx        xxx  xxx

"6. In the case at bar, even granting that the late Manuela Buenavista's execution of the documents referred to as Exhibits A, C and D are valid, nevertheless its validity ceases from the time that she executed the Last Will and Testament x x x because the execution of the Last Will invalidates the former act of the said Manuela Buenavista;

"7. That the Last Will and Testament x x x which is now pending probate in the Municipal Trial Court of Vinzons, Camarines Norte, will finally affect the property - hence, there is a ground for this motion for reconsideration and/or to suspend the decision - pending final outcome of the probate of the last will and testament of the late Manuela Buenavista." (pp. 88-89, Rollo.)

Private respondents opposed the Motion for Reconsideration asserting that the partition inter vivos which had been implemented long before the execution of the said Last Will and Testament could not be revoked by the later instrument; that the supposed Last Will and Testament was executed on December 11, 1969, more than one year after the filing of the complaint for annulment on October 9, 1968, when said Manuela Buenavista was already senile and not of disposing mind; that while Manuela Buenavista was able to sign with her own hand the several Deeds of Sale, the supposed Last Will and Testament bears her thumbmark only; that Manuela Buenavista had no more property to dispose of by will on December 11, 1969, when she supposedly executed her Last Will and Testament.

On June 28, 1984, the Appellate Court denied the Motion for Reconsideration.

In their petition for review of the decision of the Court of Appeals, the petitioners allege:

"(1) That the Intermediate Appellate Court (now Court of Appeals) erred in declaring valid the deeds of sale (Exhs. A, B, C and D) as a partition by an act inter vivos considering that examining the said exhibits will reveal that it is not a testament amounting to a will of Manuela Buenavista;

"(2) That the Intermediate Appellate Court erred in ruling against Article 1347 of the New Civil Code." (p. 126, Rollo.)

We find those contentions not well-taken.

Article 1080 of the New Civil Code allows a person to make a partition of his estate either by an act inter vivos or by will and such partition shall be respected insofar as it does not prejudice the legitime of the compulsory heirs.  While the law prohibits contracts upon future inheritance, the partition by the parent, as provided in Art. 1080, is a case expressly authorized by law (Art. 1347, par. 2, Civil Code of the Phil. by Padilla, 1987 Edition, p. 744.) Art. 1080 of the Civil Code clearly gives a person two options in making a partition of his estate:  either by an act inter vivos or by WILL.  When a person makes a partition by will, it is imperative that such partition must be executed in accordance with the provisions of the law on wills; however, when a person makes the partition of his estate by an act inter vivos, such partition may even be oral or written, and need not be in the form of a will, provided that the partition does not prejudice the legitime of compulsory heirs.

"In numerous cases it has been held or stated that parol partitions may be sustained on the ground of estoppel of the parties to assert the rights of a tenant in common as to parts of land divided by parol partition as to which possession in severalty was taken and acts of individual ownership were exercised.  And a court of equity will recognize the agreement and decree it to be valid and effectual for the purpose of concluding the right of the parties as between each other to hold their respective parts in severalty.

"A parol partition may also be sustained on the ground that the parties thereto have acquiesced in and ratified the partition by taking possession in severalty, exercising acts of ownership with respect thereto, or otherwise recognizing the existence of the partition." (Hernandez vs. Andal, et al., 78 Phil. 196, 203.)

In the instant case, the respondent appellate court declared the Deeds of Sale executed by Presentacion, Floserfina and Raquel, all surnamed Chavez (Exhs. A, B, and C) in favor of Concepcion Chavez as evidence of a valid partition of the land in question by and between Manuela Buenavista and her children as she not only gave her authority thereto but also signed the sales.  The Deeds of Sale (Exhs. A, B, and C) are not contracts entered into with respect to future inheritance but a contract perfected and consummated during the lifetime of Manuela Buenavista who signed the same and gave her consent thereto.  Such partition inter vivos, executed by the property owner herself, is valid.

"x x x As the defendants freely participated in the partition, they are now estopped from denying and repudiating the consequences of their own voluntary acts.  It is a general principle of law that no one may be permitted to disavow and go back upon his own acts, or to proceed contrary thereto." (Joaquin vs. Mitsumine, 34 Phil. 858.)

"Where a piece of land has been included in a partition, and there is no allegation that the inclusion was effected through improper means or without the petitioner's knowledge, the partition barred any further litigation on said title and operated to bring the property under the control and jurisdiction of the court for proper disposition according to the tenor of the partition. . .  They cannot attack the partition collaterally x x x." (Ralla vs. Judge Untalan, 172 SCRA 858, 865, citing the case of Torres vs. Encarnacion and De Borja, No. L?4681, July 31, 1951, 89 Phil. 678.)

As well argued by counsel for the respondents in their memorandum, it would be unjust and inequitable to allow Manuela Buenavista Vda. de Chavez to revoke the sales' she herself authorized as well as the sale she herself executed in favor of her son only to execute a simulated sale in favor of her daughter Raquel who had already profited from the sale she made of the property she had received in the partition inter vivos; it would run counter to the doctrine that "no person should be allowed to unjustly enrich herself at the expense of another."

WHEREFORE, finding no reversible error in the decision of the Court of Appeals in AC-G.R. No. CV-64708, the same is affirmed in toto.  The petition for review is dismissed for lack of merit, with costs against the petitioners.

SO ORDERED.

Narvasa, (Chairman), Cruz, Gancayco, and Medialdea, JJ., concur.