Sayyiduna Ibn Buhaynah (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) saw a man praying two rak'ahs when the iqamah for the prayer had been called, so the Prophet (peace and blessings be upon him) said: "Is the morning prayer four rak'ahs? Is the morning prayer four rak'ahs?"
Ya'qub said: This is the correct version, and Ibrahim erred in saying "from his father."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4540