John Gill Commentary Deuteronomy 7:12

"And it shall come to pass, because ye hearken to these ordinances, and keep and do them, that Jehovah thy God will keep with thee the covenant and the lovingkindness which he sware unto thy fathers:" — Deuteronomy 7:12 (ASV)

Wherefore it shall come to pass, if you hearken to these
judgments, and keep and do them
Attentively listen to the declaration made of them, and be careful to observe them:

that the Lord your God shall keep unto you the covenant and the mercy
which he swore unto your fathers ;
to bring them into the land of Canaan, and continue them in it; yea, to send the Messiah to them, and bring him the salvation of Israel out of Zion; see (Luke 1:68–73) .