Rashi on Exodus 12:25/רש"י על שמות י״ב:כ״ה

1והיה כי תבאן אל הארץ AND IT SHALL COME TO PASS WHEN YE BE COME TO THE LAND — Scripture makes the observance of this service dependent upon their entrance into the land of Palestine (Mekhilta), and they were not under any obligation, when in the wilderness, to keep more than the one Passover which they kept in the second year after the Exodus (cf. Numbers 9:1—5), and that, too, only in consequence of a special divine communication. (Cf. Rashi on Numbers 9:1 and כאשר דבר (תוס׳ קיד׳ ל"ז ע"ב ד"ה הואיל

2ACCORDING AS HE SPAKE — And where did He say that He would give them that land? In the following verse: (Exodus 6:8) “And I will bring you into the land” (Mekhilta).