Albert Barnes Commentary Psalms 135:4

"For Jehovah hath chosen Jacob unto himself, [And] Israel for his own possession." — Psalms 135:4 (ASV)

For the Lord has chosen Jacob for himself — The descendants of Jacob. He has selected them from among all the inhabitants of the earth to be his special people.

And Israel for his peculiar treasure — The word here rendered "treasure," means that which is acquired; property; wealth. They were what God possessed, owned, or claimed among all the people of the earth as especially his own. He had chosen them; he had redeemed them; he had made them his own, and he regarded them with the interest with which anyone looks on his own property, the fruit of his own toil. See Exodus 19:5; Deuteronomy 7:6; Deuteronomy 32:9; 1 Kings 8:53.