Why did the Commander of the Faithful, Umar, may Allah be pleased with him, say, after Uqbah ibn Amir recited Surah Bara'ah to him: "I did not think it had been revealed"?

Umar said that in astonishment at Uqbah's beautiful recitation of the Holy Quran, as if he had never heard it before, due to how deeply affected he was by it. Al-Baqillani believes that Umar said that because of the freshness and novelty he found in Uqbah's excellent recitation, and the fear and trepidation it renewed and caused within him, similar to what someone might say: "It's as if I've never recited it or heard it before." And whoever thinks that Umar did not know that Surah Barā'ah had been revealed, then he is the foolish, deluded one. Al-Dhahabi said: Its meaning is, "It's as if I had not heard it before," due to the beauty with which Uqbah embellished it with his recitation.