He said that the Prophet used to fast on Mondays and Thursdays, and when someone remarked on this to him he said, “On Monday and Thursday God forgives every Muslim except two who are at variance, for He says they must be left till they make peace with one another.” Ahmad and Ibn Majah transmitted it.
Hadith Referenceمشكوة المصابيح / كتاب الصوم / 2073
Hadith Gradingالألبانی:لم تتمّ دراسته | زبیر علی زئی:إسناده حسن
Hadith Takhrij´تحقيق و تخريج: محدث العصر حافظ زبير على زئي رحمه الله` «إسناده حسن، رواه أحمد (329/2 ح 8343) و ابن ماجه (1740)»