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