Musar zu Ijow 22:23

Therefore we pray and purify our hearts to serve Thee in truth, that we should do all of our service in truth, and we should believe with a complete heart and with a soul that desires, and our faith should not be something that we demonstrate only before people, or because of money matters or because we are in distress. And that is what is said, "If thou return to the Almighty, thou shalt be built up" (Job 22:23). For when no thought divides you from the Almighty, then you will build with a mighty building in the radiant light of the Divine Presence. Therefore David said, "Lord, who shall sojourn in Thy tabernacle? Who shall dwell upon Thy holy mountain? He that walketh uprightly, and worketh righteousness, and speaketh truth in his heart" (Ps. 15:1—2). And he did not say, "He who speaks the truth in his mouth," for what he meant was that the truth should be deeply rooted and established in the heart of man. Therefore, when the pious men of old had some object to sell, they would sell it to the purchaser for the price they had already determined in their mind, and even if the purchaser wanted to pay more, they did not want anything except what their heart had already decided to accept. If an esteemed person who follows this path of speaking the truth in his heart, makes up his mind to do a certain thing, he should write down that thought in order not to forget it, and he should not break the promise made in his thought. And if he is unable to fulfill it, let him go to a Sage, who will absolve him of the promise made in his thoughts. And he may vow that nothing in his thoughts shall be considered binding so long as he does not utter it with his mouth.