Leviticus 23:9 - Ellicott's Commentary On The Whole Bible

And the Lord spake unto Moses. — As the celebration of the sheaf of first-fruits formed no part of the original institution of the Passover (Exodus 12:1-20), and as the omer ritual could not be observed in the wilderness, where there was no sowing of corn, it is here enacted as a prospective part of the feast of unleavened bread, and hence is introduced by a separate formula.