For the source text click/tap here: Sukkah 39
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Tosfos rules that one who took the lulav and did not recite the blessing can still do so as long as he has not yet waved the lulav. Although one can fulfill the mitzvah of lulav without waving it, the mitzvah is not deemed to be complete until he waves the lulav. This follows the principle that one can recite a blessing for a mitzvah as long as he has not completed the mitzvah. Thus, one can recite the blessing of netilas yadayim after washing his hands because the mitzvah is not deemed to be complete until one dries his hands.
Rav Judah used the word “over” to mean “before,” in his statement about blessing before a mitzvah. Evidently, the rabbis sense that this is an unusual use of the word. Therefore, they try to look for biblical precedent for the word used in this manner, to mean “before.” They find three verses in which the word or the root עבר is used to mean to go before.
One example of this is regarding the laws of inheritance, where it is said, vhaavartem es nachalaso lebito, and you shall cause his inheritance to pass over to his daughter. The Gemara derives from the usage of the word vhaavartem that HaShem is angered by one who does not leave over a male child to inherit his estate. The same interpretation can be applied here.