מדרש אויף תהילים 119:106

R. Gidel in the name of Rab said (Fol. 8) "Whence do we infer that one may bind himself with an oath to perform a commandment? It is said (Ps. 119, 106) I have sworn, and I will perform, etc." Behold every one is bound by the Sinaic oath to perform the commandments? We must therefore say that he means it is proper to swear [to perform a religious act] in order to urge upon himself its fulfillment. R. Gidel in the name of Rab said further: "Whoever says to his associate, let us get up in the morning and study this chapter, the one that proposed it is supposed to get up first, as it is said (Ezek. 3, 22) And He said unto him, arise, go forth into the valley, etc. And I arose, and went forth into the valley; and, behold, there was the glory of the Lord standing."

Another thing from you, God. Solomon said (Proverbs 25:25) "Cool water to a weary soul". David was tired and his soul yearned to be in the Temple, as it says (Psalms 26:8) "I love the house where you dwell" and (Psalms 84:3) "My soul longed, and even pined for the courts of God". (Psalms 27:4) "One thing I ask from the Lord, this only do I seek: that I may dwell in the house of the Lord all the days of my life". God said to him, "You don't know who will ascend the mountain of the Lord." He should keep his hands clean and his heart pure. One who possesses these two qualities should immediately be happy and say "I have them". As it says (1 Samuel 13:14) "The Lord has sought out a man after his own heart". Therefore it is said, "Cool water to a weary soul." And it says (Psalms 119:106) "I have sworn and confirmed that I will keep your righteous laws." He receives two rewards: the reward for action and the reward for oath. Therefore it is said of you, "I have trusted." Rabbi Yitzhak said, "In your Torah there are twenty-two letters."