Midrash for Bekhorot 105:4

"your tithes": R. Akiva says: Scripture speaks of two tithes, the grain tithe and the animal tithe.

R. Akiva says: I might think that one brings firstlings from outside of Eretz Yisrael to the land (to be sacrificed); it is, therefore, written (Ibid.) "And you shall eat before the L-rd your G-d, in the place that He shall choose to repose His name there the tithe of your corn … and the firstlings." From the place whence you bring the corn tithe (i.e., Eretz Yisrael) you bring firstlings. From outside Eretz Yisrael, whence you do not bring the corn tithe, you do not bring firstlings.