Sayyiduna Umar (may Allah be pleased with him) narrates that once during the Prophetic era, I passed by Hisham bin Hakeem while he was reciting Surah Al-Furqan. He recited certain letters in it which the Prophet (peace and blessings be upon him) had not taught me. I wished to question him about it right there in the prayer, then he mentioned the complete hadith.