Exodus 3:12

3:12 He replied, “Surely I will be with you, and this will be the sign to you that I have sent you: When you bring the people out of Egypt, you and they will serve God on this mountain.”

Exodus 13:9

13:9 It will be a sign for you on your hand and a memorial on your forehead, so that the law of the Lord may be in your mouth, for with a mighty hand the Lord brought you out of Egypt.

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.

Exodus 31:17

31:17 It is a sign between me and the Israelites forever; for in six days the Lord made the heavens and the earth, and on the seventh day he rested and was refreshed.’”