ALLAH 
SAYS: “And fulfil (every) promise, for (every) promise will be inquired into.” [1].
SAYS: “And fulfil (every) promise, for (every) promise will be inquired into.” [1].
Allah says: “And those who, when they make a pledge, fulfil their pledges.” [2].
says: “And those who, when they make a pledge, fulfil their pledges.” [2].
We relate in the book of Ibn as-Sunnī from Khawāt ibn Jubayr 
who said: “The Messenger of Allah 
visited me when I had been sick. He said: ‘The body has recovered, Khawāt.’ I said: ‘And your body, Messenger of Allah.’ He said: ‘Fulfill the promise you have made to Allah.’ I said: ‘I did not promise Allah anything.’ He said: ‘Yes, you did; for no one becomes sick who fails to, speaks to Allah about good. So fulfil what you have promised Allah.’” [3].
who said: “The Messenger of Allah visited me when I had been sick. He said: ‘The body has recovered, Khawāt.’ I said: ‘And your body, Messenger of Allah.’ He said: ‘Fulfill the promise you have made to Allah.’ I said: ‘I did not promise Allah anything.’ He said: ‘Yes, you did; for no one becomes sick who fails to, speaks to Allah about good. So fulfil what you have promised Allah.’” [3].References
[1] Qur’ān 17:34
[2] Qur’ān 2:177.
[3] Ibn as-Sunnī (563).