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." (DE)
App reference (DE): Book 14, Hadith 66 (DE)
English reference (DE): Vol. 2, Book 14, Hadith 1430 (DE)
Arabic reference (DE): Book 14, Hadith 1440 (DE)