“Abdul Aziz said: 962 – Abu Abdillah said in the narration of Abdillah: from Nāfi’, from Ibn ‘Umar, he said:
The Messenger of Allah ﷺ said: “The month is 29 days, so do not fast until you see it (the new moon), and do not break the fast until you see it, and if it is obstructed from you, then account for it.” Nāfi’ said: So Abdullah bin ‘Umar, when it was the night of the 30th of Sha’bān, would send someone to look, so if there were clouds in the sky or fog or dust, he would be fasting the next day, and if the sky was clear, no clouds, fog or dust, he would not fast the next day.