Imran b. Husain (Allah be pleased with them) reported that Allah's Apostle (ﷺ) said to a person: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

English translation · Sahih Muslim