Matthew Poole and continuators on Psalms 77:15

15 Thou hast with thine arm redeemed thy people , the sons of Jacob and Joseph , Selah.

To wit, out of Egypt after a long and hard Bondage. Which he here mentions to strengthen his Faith in their present Captivity.

Whom he mentions; Partly, as a most Eminent Portion of the sons of Iacob, branched forth into two numerous Tribes: Partly, because the sons of Ioseph were born in Egypt, which Iacob's other Sons were not: and Partly, because he laid the Foundation of that Redemption, by bringing them into Egypt, and preserving and nourishing Iacob and his Sons there, as a little Child is nourished, as it is expressed in the Hebrew Text, Gen. 47. 12. In which respect he was a second Father to them, and they might well be called his Sons; without whose Care (to speak humanely) there had been no such Redemption, nor People to be redeemed.

Marginal references: Exod. 6. 6.