These words are to be understood of sins willfully, contumaciously and presumptuously committed and the petition supposes, that these may be committed by ‘good’ men, if left to themselves and that there is a proneness in them to sin and that they would rush into them, were they not kept back and restrained by the powerful and Efficacious Grace of God. It also supposes that the saints cannot keep themselves; that God only can keep them from evil and therefore they pray to Him that He would and Who does keep them by His Power, at least from a final and total falling away.