הלכה על ביכורים 1:6

And they, may their memory be blessed, said (Mishnah Bikkurim 1:6) that one who acquires two trees within his fellow's field brings [them] but does not recite, as they were in doubt in the Gemara (Bava Kamma 81b) whether one who acquires two trees [receives] the land or not. But one who acquires three [trees] brings and recites. [These] and the rest of the details of the commandment are elucidated in Tractate Bikkurim and in the seventh chapter of Sotah.