It was narrated from Ibn 'Umar that:
He used to pray two rak'ahs after jumu'ah, making them lengthy, and he said: "The Messenger of Allah (ﷺ) used to do this."
App reference: Book 14, Hadith 66
English reference: Vol. 2, Book 14, Hadith 1430
Arabic reference: Book 14, Hadith 1440