Imitation of Christ

Qui nullum extrinsecus pro se testimonium quærit, liquet quod Deo se totaliter commisit. Non enim, qui se ipsum commendat, ille probatus est, ait beatus Paulus, sed quem Deus commendat. Ambulare cum Deo intus, nec aliqua affectione teneri foris, status est interni hominis. 

He who seeks no outward witness on his own behalf, shows plainly that he has committed himself wholly to God. For not he that commends himself is approved, as St. Paul saith, but whom the Lord commends. To walk inwardly with God, and not to be held by any outer affections, is the state of a spiritual man.

Imitation of Christ, II, 5:4