Praise be to Allah.
If one is reciting Quran in situations other than in prayer, then reading from the Mushaf is better, because it is more accurate and helps one to remember better. But if reciting from memory is easier and helps one to concentrate more and have better presence of mind (khushoo’), then one should recite from memory.
In prayer, however, it is better to recite from memory, because if a person recites from the Mushaf, he will be doing repeated actions such as holding the Mushaf, putting it down, turning its pages and looking at the letters. By doing so he will miss out on putting his right hand over his left hand on his chest when standing during the prayer, or spreading out his arms during rukoo’ and sujood, if he puts the Mushaf under his arm. Hence we think that it is preferable for a person who is praying to recite from memory rather than from the Mushaf.
We see some people when they pray behind the imaam, carrying the Mushaf and following the imaam’s recitation. This is something which should not be done, for the reasons we have referred to above, and because they do not need to do anything except follow the imaam.
However, if the imaam does not have such a good memory, and he says to one of the members of the congregation, “Pray behind me, and follow me (my recitation) in the Mushaf, and if I make a mistake, correct me,” then there is nothing wrong with this.