Observe fast on sighting it (the new moon) and break (fast) on sighting it (the new moon), but if the sky is cloudy for you, then complete the number (of thirty).

Observe fast on sighting it (the new moon) and break it on sighting it. But if (due to clouds) the actual position of the month is concealed from you, you should then count thirty (days).

"the Messenger of Allah said: 'Fast when you see it and stop fasting when you see it, and if it is obscured from you (too cloudy), then count it as thirty (days). "'

: "The Messenger of Allah said: 'Fast when you see it and stop fasting when you see it, and if it is obscured from you (too cloudy), then count it as thirty (days).'"

Abu Huraira reported God’s messenger as saying, “Fast when you see it and break your fast when you see it, and if the weather is cloudy treat Sha‘ban as having thirty days.” (Bukhari and Muslim.)

"The Messenger of Allah said; 'Fast when you see it and stop fasting when you see it, and if it is obscured from you (too cloudy), then complete thirty (days)."'

"Fast when you see it, and stop fasting when you see it, and if clouds prevent you from seeing it, then complete the number, and do not fast ahead of Ramadan."

The Messenger of Allah (PBUH) said, "Do not observe Saum (fasting) before the advent of Ramadan. Observe Saum at sighting of the crescent of Ramadan and terminate it at sighting the crescent (of Shawwal). If the sky is overcast, complete (the month as) thirty (days)."

[At- Tirmidhi].

The Messenger of Allah (PBUH) said, "Observe Saum (fast) on sighting the crescent and terminate it on sighting it (the new moon), but if the sky is cloudy before you, then complete the number (thirty days) of the month."

[Al-Bukhari and Muslim].

'Abdur-Rahman bin Zaid bin Al-Khattab addressed the people on the day concerning which there was doubt (as to whether the month had begun) and said: "I sat with the Companions of the Messenger of Allah and asked them, and they a narrated that the Messenger of Allah said: 'Fast when you see it and stop fasting when you see it, and perform the rites on that basis. If it is obscured, then complete thirty days, and if two witnesses testify then fast and stop fasting."

the Messenger of Allah said: "Do not fast before Ramadan. Fast with its sighting, and break fast with its sighting, and if it is obscured from you, then complete thirty days."

"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." '

the Prophet said: "Do not precede the month with a day nor with two days, unless that fast falls on a day that one of you would have (normally) fasted. Fast with its sighting and break fast with its sighting, and if it is cloudy, then count for thirty days, and then break (the fast)."