Sh. Al-Allamah Salih Al-Fowzan, hafidahu’Allah (may Allah preserve him), was asked, 
Q: “What is the ruling of reciting the Quran in a beautiful voice when giving the khutbahs or lectures?”
A: “Questions regarding this matter are plenty because some of the brothers recite verses beautifully in the khutbah or in reminders and this [affair] is something not known with the salaf. Because there is a difference between reciting the Quran [with tarteel] and reciting for the purpose of providing proof. Reciting the Quran is done with the rulings of recitation and recited slowly. As for reciting the [Quran] when bringing proof then it is not to be recited in a beautiful manner, rather it is recited properly without any mistakes.”
Al Ijabaat Al Muhimmah fiil Masyakil Al Mulimmah, pg 278-279
Translated by 

Abu Aisha Yassin