'It is I' in the Bible

For it is impossible for those who have once for all been enlightened and have experienced the gift from heaven, who have been made sharers of the Holy Spirit

and then have fallen by the wayside -- it is impossible, I say, to keep on restoring them to their first repentance, since they continue to crucify the Son of God to their detriment and hold Him up to contempt.

so that by these two unchangeable things in which it is impossible for God to prove false, we who have taken refuge with Him may have encouragement strong enough to make us seize upon the hope that lies ahead of us.

but without faith it is impossible to please Him, for anyone who approaches God must believe that there is a God and that He gives rewards to all who earnestly try to find Him.