The Messenger of Allah ﷺ said, "When the prayer is announced, do not stand until you see that I have come out."
أخبرنا الحسين بن حريث قال حدثنا الفضل بن موسى عن معمر عن يحيى بن أبي كثير
قال رسول الله ﷺ إذا أقيمت الصلاة فلا تقوموا حتى تروني خرجت
Muslim transmitted it, Mosques, chapter on when people should stand for prayer, hadith 156/604, from the hadith of Mamar. Bukhari transmitted it, Adhan, chapter on when people should stand when they see the imam at the iqamah, hadith 637, from the hadith of Yahya, through the same chain. It is also found in Kubra, hadith 1651.