Peter, in particular, was so struck with the miracle, that he could not forbear expressing his astonishment in the most lively manner, both by words and gestures: he fell down at Jesus’s knees — In amazement and confusion; saying, in deep self-abasement, Depart from me, for I am a sinful man, O Lord — And therefore utterly unworthy to be in thy presence.
He believed the holy God was peculiarly present with the person who could work such a miracle; and a consciousness of sin made him afraid to continue in his presence, lest some infirmity or offence should expose him to some more than ordinary punishment.
Observe here, reader, 1st, Peter’s acknowledgment was very just, and one which it becomes us all to make, I am a sinful man, O Lord: for even the best of men are sinful men, and should be ready upon all occasions to own it, and especially to own it to Jesus Christ; for to whom else but to him, who came into the world to save sinners, should sinful men apply themselves?
2d, His inference from it was not just: if we be sinful men, as indeed we are, we should rather say, “Lord, for that very reason, while we own ourselves most unworthy of thy presence, we most importunately entreat it: Come unto me, O Lord, for I am a sinful man, and if thou stand at a distance from me, I perish! Come and recover my heart from the tyranny of sin; come and possess it, and fix it for thyself.”
But, considering what reasons sinful men have before the holy Lord God to dread his wrath, Peter may well be excused in crying out, on a sudden, under a sense of his sinfulness and vileness, Depart from me, O Lord. Though Peter was the only person who spake on this occasion, the rest were not unaffected. James and John, who were partners with him — Were also struck with astonishment, and, doubtless, were also humbled before him.
[Excerpt from the Benson Commentary]