Deuteronomy 27:9

And Moses and the priests the Levites spake unto all Israel, saying, Take heed, and hearken, O Israel; this day thou art become the people of the Lord thy God.

Cross-reference

Deuteronomy 26:16-18 similarly declares Israel as the LORD's treasured people after obeying His commands — reinforcing this covenant status.

1 Peter 2:10 directly echoes 'once not a people, now God's people' — a clear NT application of the Deut 27:9 declaration.

In 2 Samuel 7:24, the same covenant language appears—God establishing Israel as His people forever, echoing this declaration.