Zayd bin Wahb (may Allah have mercy on him) said: Two men came to Sayyiduna Abdullah (may Allah be pleased with him), while we were with him, and one of them said: "O Abu Abd al-Rahman, how should we recite this verse?" Sayyiduna Abdullah (may Allah be pleased with him) recited it to him. The man said: "But Abu Hakim taught me to recite it in such and such a way." The narrator said: And the other recited it his own way. Sayyiduna Abdullah (may Allah be pleased with him) asked: "Who taught you to recite it?" He said: "Umar (may Allah be pleased with him)." Sayyiduna Abdullah (may Allah be pleased with him) said: "Recite it as Umar (may Allah be pleased with him) taught you." Then Sayyiduna Abdullah (may Allah be pleased with him) wept so much that I saw his tears dripping onto the pebbles. Then he said: "Indeed, Umar (may Allah be pleased with him) was a strong fortress for Islam; people would enter it and not leave. Now that fortress has been breached, and people leave it and do not enter."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 8772