Shaylh Ibn Uthaymeen was asked the following question:
Question:
What is the ruling on fulfilling promises?
Answer:
“According to the mathhab, it is Sunnah and what is correct is that it is obligatory”.
[Kanz uth-Thameen Fi Su’alaat Ibn Saneed no. 760 pg. 175]
Translated by
Faisal Ibn Abdul Qaadir Ibn Hassan
Abu Sulaymaan