question #3 Sahih Muslim 1161c, Book 13, Hadith 258 : What guidance did the Prophet Muhammad (ﷺ) provide regarding fasting outside of Ramadan?

Did you observe any fast in the middle of this month (Sha’ban)? He said: No. Thereupon the Messenger of Allah (ﷺ) said: Fast for two days instead of (one fast) when you have completed (fasts of) Ramadan.