question #1 Sahih Muslim 936b, Book 11, Hadith 42 : What is the significance of making and fulfilling pledges in Islam?

Umm ‘Atiyya reported that the Messenger of Allah (ﷺ) took pledge from us (including this promise) that we would not lament. Only five amongst us fulfilled the promise, and one of them (who fulfilled the promise) was Umm Sulaim.