Charles H. Spurgeon on Psalms 77:15

Thou hast with thine arm redeemed thy people, the sons of Jacob and Joseph. All Israel, the two tribes of Joseph as well as those which sprang from the other sons of Jacob, were brought out of Egypt by a display of divine power, which is here ascribed not to the hand but to the arm of the Lord, because it was the fulness of his might. Ancient believers were in the constant habit of referring to the wonders of the Red Sea, and we also can unite with them, taking care to add the song of the Lamb to that of Moses, the servant of God. The comfort derivable from such a meditation is obvious and abundant, for he who brought up his people from the house of bondage will continue to redeem and deliver till we come into the promised rest. Selah. Here we have another pause preparatory to a final burst of song.