Exodus 4:4

4:4 But the Lord said to Moses, “Put out your hand and grab it by the tail” – so he put out his hand and caught it, and it became a staff in his hand –

Exodus 31:13

31:13 “Tell the Israelites, ‘Surely you must keep my Sabbaths, for it is a sign between me and you throughout your generations, that you may know that I am the Lord who sanctifies you.