It is narrated from Sayyiduna Abdullah (may Allah be pleased with him) that he said: "The waiting period ('iddah) of a divorced woman begins from the time she is divorced, and that of a widow from the time her husband dies. And whoever wishes, I am ready to swear an oath against him that the shorter Surah al-Nisa was revealed after Surah al-Baqarah."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9609