Rashi on Deuteronomy 26:1/רש"י על דברים כ״ו:א׳

1והיה כי תבוא … וירשתה וישבת בה AND IT SHALL BE, WHEN YOU COME IN [UNTO THE LAND …] AND POSSESS IT AND SETTLE THEREIN — This tells us that they (the Israelites) were not under the obligation to bring first fruits until they had conquered the land and divided it (cf. Kiddushin 37b).