Charles Spurgeon Commentary Acts 2:28-29

"Thou madest known unto me the ways of life; Thou shalt make me full of gladness with thy countenance. Brethren, I may say unto you freely of the patriarch David, that he both died and was buried, and his tomb is with us unto this day." — Acts 2:28-29 (ASV)

You have made known to me the ways of life; you will make me full of joy with your countenance. Men and brethren, let me freely speak to you of the patriarch David, that he is both dead and buried, and his sepulcher is with us to this day.

Peter craves the liberty to speak freely, and then, to win their attention and approval, he very shrewdly gives David the high title of patriarch, which is not generally given to him, saying: Let me freely speak to you of the patriarch David, that he is both dead and buried, and his sepulcher is with us to this day, and therefore he was not speaking about himself in the words Peter was quoting.