A very important reference:
فأما كعب بن لؤي، فكان أعظم ولد أبيه قدرا، وأعظمهم شرفا، وكان أول من سمي يوم الجمعة بالجمعة، وكانت العرب تسميه عروبة، فجمعهم فيه، وكان يخطب عليهم، فيقول: اسمعوا، وتعلموا، وافهموا، واعلموا أن الليل ساج، والنهار ضاح، والأرض مهاد، والسماء عماد، والجبال أوتاد، والنجوم أعلام، Ka'ab Bin Lowy was a man of great honour among his ancestors and progeny. He was the first person who gave the name of Friday to the day of Friday. Arabs used to call him 'Aroba. He gathered them and advised them to hear, learn and understand, and to know that night is deserted and silent, while day is full of sunlight, and earth is a cradle while sky is a support, and mountains are pegs, and stars are signs, ...
Kamranlashari (talk) 17:50, 17 June 2021 (UTC)