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, and save me - Were there no human agents or earthly means that he could employ, he would send his angels from heaven to rescue me from my enemies. Or, He will give his command from heaven that this may be done on earth.
Selah - I think this word should be at the end of the verse.
God shall send forth his mercy and his truth - Here mercy and truth are personified. They are the messengers that God will send from heaven to save me. His mercy ever inclines him to help and save the distressed. This he has promised to do; and his truth binds him to fulfll the promises or engagements his mercy has made, both to saints and sinners.