Abu Hurairah (May Allah be pleased with him) reported:
The Messenger of Allah (ﷺ) said, "The best month for observing Saum (fasting) next after Ramadan is the month of Allah, the Muharram; and the best Salat (prayer) next after the prescribed Salat is Salat at night (Tahajjud prayers)."[Muslim]. (ES)
App reference (ES): Book 9, Hadith 256 (ES)
Arabic/English book reference (ES): Book 9, Hadith 1246 (ES)