Midrash su Ezechiele 17:5

Rabbi Ẓe'era taught: The tree || which is mentioned here is none other than the vine tree. If they do not cut off from the tree the fruit of the first three years, all the fruit which it yields will be gleanings fit to be pluckt off, and not good; and its wine will be disqualified for the altar; but if they cut off from the tree the fruit of the first three years, all the fruit which it yields will be good for the sight, and their wine will be selected to be brought upon the altar. So with our father Abraham; before he was circumcised, the fruit which he produced was not good [in its effects, and was disqualified from the altar; but when he had been circumcised, the fruit which he produced was good in its effects, and his wine] was chosen to be put upon the altar like wine for a libation, as it is said, "And wine for the drink offering" (Num. 15:5).