ʿUmar’s directive to pray eleven rakʿahs:

As for ʿUmar’s instruction—may Allah be pleased with him—to have the prayer performed in eleven rakʿahs, it is the report transmitted by Mālik in the Muwaṭṭaʾ (1/137, no. 248) from Muḥammad ibn Yūsuf, from al-Sāʾib ibn Yazīd, who said:

“ʿUmar ibn al-Khaṭṭāb, may Allah be pleased with him, ordered Ubayy ibn Kaʿb and Tamīm al-Dārī to lead the people in eleven rakʿahs. The reciter would read surahs of a hundred or more verses, so we would lean on staffs because of the length of the standing, and we would not disperse until the break of dawn.”

Its chain of transmission is exceedingly sound, and Ibn Isḥāq has also narrated it. ⦗53⦘