If a person knows the most Quran out of a group of people, he should lead the Salah, but what if he didn't want to lead because he knows him self. He knows that he most likely will do Reah (wind), which is when leading his intention will change for other then Allaah. Is this person allowed not to lead the Salah? For fear of Reah.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

Since this person is afflicted by frequently passing wind, then there is no harm on him, Inshaa' Allaah, in not leading the congregation in prayer, and it might be that this is better as the scholars differed in opinion with regard to the permissibility of a person who has urine incontinence in leading the prayer and others to whom the same ruling apply. Some scholars are of the view that it is disliked but permissible for a healthy person to be led in prayer by a person who has some health inconsistencies. However, some other scholars are of the opinion that it is not acceptable or permissible for a healthy person to be led by someone who has some health inconsistencies; this is the view of the Hanafi school. Ibn Al-Humaam from the Hanafi school, said: 'A person in a state of purity should not pray behind a person who is in a state similar to that of a woman who has irregular blood discharges, like a person who has urine incontinence or passes wind without his control.' Moreover, Haafith Ad-Deen An-Nasfi from the Hanafi school said: 'It is not valid for a person who is [generally] in a state of purity to be led by a person who has excuses for invalidating his purity.'

Therefore, in order to avoid this difference in opinion, it is more appropriate for a person who has a valid reason [for not leading the prayer], like urine incontinence or passing wind and the like, not to lead the prayer. Nonetheless, if the person you are asking about has no sound reason, like passing wind and so forth, but refuses to lead the prayer just because of whispers and doubts then he should not refrain from leading the prayer if he is the most knowledgeable in reciting the Quran. 

Allaah Knows best.