Sforno on Deuteronomy 26:4/ספורנו על דברים כ״ו:ד׳

1והניחו לפני מזבח ה' אלוקיך, to make plain by this gesture that these fruit are not really intended for the priest, but are a present to G’d, Who, in turn, gives them to the priest just as He does with other offerings brought to Him.