四分律行事鈔資持記 2.1464

2.1464

振手戒。（譏云無有正法，如王大臣。）未受食污手，或容粘綴故。

The precept against shaking the hands. (The censure says, 'Having no correct Dharma, like kings and great ministers.') Before receiving food, it might soil the hand, or something might stick to it, hence [shaking is prohibited].