From Sahih Muslim (Hadith 1975):
Abu Burda b. Abu Musa al-Ash'ari reported:'Abdullah b. Umar said to me: Did you hear anything from your father narrating something from the messenger of Allah (ﷺ) about the time on Friday? I said: Yes, I heard him say from the Messenger of Allah (ﷺ) (these words):" It is between the time when the Imam sits down and the end of the prayer
Reference: Muslim 1975