Sayyiduna Umar bin Khattab (may Allah be pleased with him) was one day conversing with himself in solitude, when he called Sayyiduna Ibn Abbas (may Allah be pleased with them both) and asked: "How will this Ummah differ, when its Prophet is one, its Book is one, and its Qiblah is one?" Sayyiduna Ibn Abbas (may Allah be pleased with them both) replied: "O Commander of the Faithful! The Qur'an was revealed to us, we read it and knew regarding which matters it was revealed, but after us there will come people who will read the Qur'an but will not know under what circumstances it was revealed, so each group will form its own opinion in it, and when each group has a different opinion, they will differ among themselves, and when the differences increase, they will fight each other." Upon hearing this, Sayyiduna Umar (may Allah be pleased with him) scolded him and spoke harshly, so Sayyiduna Ibn Abbas (may Allah be pleased with them both) left. Later, Sayyiduna Umar (may Allah be pleased with him) called him again, understood his words, and said: "Alright, repeat what you said."