"Do not fast one or two days ahead of the month, unless the one who used to observe a regular fast. In that case let him fast." '
Sunan an-Nasa'i Book 22, Hadith 101
← Previous Hadith "I entered upon 'Ikrimah on the day concerning which there was doubt as to whether it was Ramadan or Shaban, and he was eating bread, vegetables and milk. He said: 'Come and eat.' I said: 'I am fasting.' He adjured me by Allah to break my fast. I said Subhan-Allah twice. When I saw that he was insisting, I went forward and said: 'Give me what you have.' He said: 'I heard Ibn 'Abbas say: The Messenger of Allah said: 'Fast when you see it (the crescent) and stop fasting when you see it, and if clouds or darkness prevent you from seeing it, then complete the number of days of Shaban, and do not fast ahead of the month, and do not join Ramadan to a day of Shaban." '

Sunan an-Nasa'i Book 22, Hadith 100 Next Hadith → "Whoever spends the nights of Ramadan in prayer (Qiyam) out of faith and in the hope of reward, he will be forgiven his previous sins." '

Sunan an-Nasa'i Book 22, Hadith 102