What does the Torah mean when it writes "Lehosif lachem Tevu'aso"?
Rashi, Rashbam and Targum Yonasan: It means that whoever keeps this Mitzvah is assured of a Divine blessing, that his trees will produce a bumper harvest in the fifth year. 1
Da'as Zekenim (in Pasuk 23): The Pasuk alludes to a child who, for three years does not know how to speak; in the fourth year, he begins to read, and at age five 2 one should stuff him [with Torah] like an ox.
B'rachos, 35a: Based on the Gezeirah Shavah "Tevu'aso" "Tevu'as ha'Kerem" Devarim, 22:9, regarding Kil'ayim, we learn that the Din of Neta R'vai is confined to the fruit of a vineyard. 3
Sifra: "Tevu'aso" teaches us that one may only redeem Neta R'vai after it is called 'Tevu'ah''Tevu'ah' (when it is fully ripe and is subject to Ma'asros). 4
Why does the Torah insert "Ani Hashem Elokeichem" here?
Rashi: To assure the owner that, having promised him reward for observing the Mitzvah of Neta Revai, that reward is forthcoming.