Fiqh-us-Sunnah Volume 1, Purification and Prayer, Fiqh 1.144A.

It is sunnah to make one’s voice beautiful and nice while reciting the Qur’an. The Prophet, upon whom be peace, said, “Beautify your voices with the Qur’an.” He also said, “He is not one of us who does not chant the Qur’an,” “The one with the best voice with the Qur’an is the one that when you hear him, you feel that he fears Allah,” and “Allah never listened to anything like he listened to his Prophet chanting the Qur’an with a beautiful voice.”

Says an-Nawawi, “It is sunnah for anyone who is reciting the Qur’an, whether he is praying or not, to ask Allah for His blessings when he comes to a verse of mercy. When he comes to a verse (describing) punishment, he should seek refuge in Allah from Hellfire, punishment, evil, from what is hated, or he may say, “Allah, I ask You for well-being, etc.” When he comes to a verse that glorifies or exalts Allah, he should say, “Glory be to Allah,” or “Blessed be Allah, the Lord of the Worlds,” and so on. Huzhaifah ibn al-Yaman is reported to have said, “I prayed with the Prophet, upon whom be peace, one night, and he started reading al-Baqarah. I said to myself, ‘He will bow after one hundred verses,’ but he continued. Then I said, ‘He will complete it and bow,’ but he moved to recite very slowly al ‘Imran and then an-Nisa’. When he came to a verse glorifying Allah, he would glorify Him. If he came to a verse that mentioned a request, he would request it. If he came to something that (one should) seek refuge from, he would seek refuge.” This was related by Muslim. Among the Shafiyyah, the glorifying, requesting and seeking refuge should be done during the prayer and at other times. The imam, followers and one praying by himself should all do so, for they are supplications that one should say, like ‘ameen. It is preferred that when reading, “Is not Allah the most conclusive of all judges?” / at-Tin:8 / one should say, “Certainly, and I am one of the witnesses to that. When one reads, “Is not He (who does so) able to bring the dead to life? / al-Qiyamah:40 /, he should say, “Certainly, and I bear witness (to it).” When one reads, “Glorify the name of your Lord, the Most High,” (al-A’la: 1), he should say, “Glory to my Lord, the Most High.” That should be said during prayer and otherwise.