Deuteronomy 29:13-15

13that He may establish you today as a people for Himself, and that He may be God to you, just as He has spoken to you, and just as He has sworn to your fathers, to Abraham, Isaac, and Jacob.

14“I make this covenant and this oath, not with you alone,

15but with him who stands here with us today before the Lord our God, as well as with him who is not here with us today