She was asked about the fasting of the Messenger of Allah ﷺ. She said, "He used to fast in Shaban and would seek out Mondays and Thursdays."
حدثنا هاشم بن القاسم قال حدثنا الأشجعي عن سفيان عن ثور عن خالد بن معدان
أنها سئلت عن صوم رسول الله ﷺ قالت كان يصوم شعبان ويتحرى الاثنين والخميس
Its isnad is sahih. Ashjai is Ubaydullah bin Abdul-Rahman Ashjai, a reliable and firm narrator, whose hadith appears in the Sahihayn. The hadith was narrated by Tirmidhi 3/112, no. 745, who said, hasan gharib, and Nasai 4/152, no. 2186, and Ibn Majah 1/553, no. 1739, all in the chapter on fasting, what has been said about fasting on Monday and Thursday.