Commentary for Deuteronomy 26:4

ולקח הכהן המנה מידך AND THE PRIEST SHALL TAKE THE BASKET OUT OF THY HAND in order to wave it. The priest places his hand beneath the hands of the owner and so waves it (Sukkah 47b).

והניחו 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.

Places his hand below the owner’s hand and waves. I already explained [how Rashi knows this] in parshas Tzav (Vayikra 7:30) and in parshas Tetzaveh (Shmos 29:24) and in parshas Emor (Vayikra 23:11). His proof is that it should have said, “The kohein shall then take the basket and place it before the altar of Adonoy, etc.” Why does it say “from your hand”? Thus “from your hand” is available for a gezeira shava. It says “hand” here and it says “hand” by the owner of a peace offering (ibid 7:30). Just as over there, there is waving, as it is specified there, so too, the “hand” over here involves waving. Regarding the waving here, Rashi explains in Chapter Lulav Ve'arava (Sukkah 47b) that the owner holds the edge of the basket while the kohein places his hands beneath the bottom of the basket. Even though regarding peace offerings, the kohein puts his hand directly under the owner’s hand, that is because a peace offering has no edge or bottom, therefore the kohein’s hand is directly under the owner’s hand.