The people looked for the moon, so I informed the Messenger of Allah ﷺ that I had sighted it. He fasted and commanded the people to fast. (Using translation from Abū Dāʾūd 2342)
«تَرَاءَى النَّاسُ الْهِلَالَ فَأَخْبَرْتُ رَسُولَ اللَّهِ ﷺ أَنِّي رَأَيْتُهُ فَصَامَ وَأَمَرَ النَّاسَ بِالصِّيَامِ»