He shall send from heaven, and save me from the reproach of him that would swallow me up. Selah. God shall send forth his mercy and his truth.
He shall send from heaven. What "He shall send" follows in the next clause.
His mercy and his truth - (cf. Psalms 18:16; Psalms 43:3; Psalms 144:7). "From heaven," my only, and my sure source of hope, as contrasted with the earth, where all is dark and dreary to me.
And save me from the reproach of him that would swallow me up -- (Psalms 56:1-2.) Calumnies, misrepresentations, and reproaches, were the stinging weapon wherewith Saul and his party assailed David (Psalms 55:12; Psalms 55:21; Psalms 56:5; cf. here Psalms 57:4, end).
Selah - a solemn pause, showing how deeply the enemy's reproaches affected him.