Is the father's statement to the paternal uncle, "My share of our father's inheritance is for you and your sons," considered a gift or a bequest to an heir, and do the daughters have the right to retract this statement, especially since it was not directly mentioned to them by the father?

Your uncle's claim that your father relinquished his share of their father's inheritance to him is merely an assertion that cannot be proven except with legitimate evidence or the confirmation of the remaining adult heirs, based on the Prophet's (peace be upon him) saying: "The burden of proof is on the claimant, and the oath is on the one who denies." Evidence can be established with one man and two women, or one man and the claimant's oath. If your uncle proves the gift with evidence, then so be it. Otherwise, you have the right to claim your father's share. However, if your uncle presents evidence of a will in his favor for your father's share, this will is not valid if your uncle is an heir, except with the consent of the adult heirs, because a will for an heir is forbidden by Islamic law.