Origen

But how can he who has been converted, and become as a little child, be yet liable to be scandalized? This may be thus explained. Every one who believes on the Son of God, and walks after evangelic acts, is converted and walks as a little child; but he who is not converted that he may become as a child, it is impossible that he should enter into the kingdom of heaven. But in every congregation of believers, there are some only newly converted that they may become as little children, but not yet made such; these are the little ones in Christ, and these are they that receive offence.