When Lady Aisha (may Allah be pleased with her) was asked about the fasts of the Messenger of Allah (peace and blessings be upon him), she said: He (peace and blessings be upon him) used to fast in the month of Sha'ban and would especially observe fasts on Mondays and Thursdays.
Hadith Referenceالفتح الربانی / كتاب الصيام / 3972
Hadith Gradingمحدثین:صحیح
Hadith Takhrij«حديث صحيح۔ اخرجه النسائي: 4/ 203، والترمذي: 745، وابن ماجه: 1649، 1739، (انظر مسند أحمد ترقيم الرسالة: 24508 ترقیم بيت الأفكار الدولية: 25013»
Brief Explanation
Benefits: … It is narrated from Sayyiduna Jabir radi Allahu anhu that the Messenger of Allah sallallahu alayhi wa sallam said: “Deeds are presented (to Allah) on Mondays and Thursdays, so whoever seeks forgiveness is forgiven, and whoever repents, his repentance is accepted. However, those who harbor malice are turned back with their malice until they repent.” (Tabarani, and Al-Mundhiri said: its narrators are trustworthy)
From this hadith, it is understood that there should also be the presence of seeking forgiveness (istighfar) and repentance (tawbah) in a servant’s record of deeds, so that he may be forgiven. From these ahadith, the virtue of fasting on Mondays and Thursdays is established. According to hadith number (3886), the Prophet sallallahu alayhi wa sallam also mentioned one reason for fasting on Monday: “That is a day on which I was born, and on it the Qur’an was revealed to me.”