Psalms 77:15

The son. of Jacob and Joseph - "The sons which Jacob begat and Joseph nourished." says the Chaldee. The Israelites are properly called the sons of Joseph as well as of Jacob, seeing Ephraim and Manasseh, his sons, were taken into the number of the tribes. All the latter part of this Psalm refers to the deliverance of the Israelites from Egypt; and the psalmist uses this as an argument to excite the expectation of the captives. As God delivered our fathers from Egypt, so we may expect him to deliver us from Chaldea. It required his arm to do the former, and that arm is not shortened that it cannot save.

Thou hast with thine arm - That is, with strength or power, the arm being a symbol of strength. Exodus 6:6; Exodus 15:16; Psalm 10:15.

Redeemed thy people - Thou didst rescue or deliver them from Egyptian bondage. See the notes at Isaiah 43:3.

The sons of Jacob and Joseph - The descendants of Jacob and Joseph. Jacob is mentioned because he was the ancestor of the twelve tribes; Joseph, because he was conspicuous or eminent among the sons of Jacob, and particularly because he acted so important a part in the affairs of Egypt, from whose dominion they were redeemed.