The Ruling on Praying Behind a Talebearer

This message is from Dr. Ahmad Muhammad Taha, a doctor at the Chest Diseases Hospital in Ta'if. He says in his message: There is a mosque in the hospital for prayer, and because the hospital is large and spacious, a small group gathers during prayer times, and one of them acts as the imam for the prayer, while they leave the mosque. There is also a group, not very large, that prays in the mosque. We doctors used to gather behind an Egyptian doctor who would pray with us in one of the hospital corridors. After a while, I discovered what the other doctors had discovered: that this imam is a man who spreads discord, speaks ill of people, and engages in talebearing. May I continue to pray behind him, or should I go to the mosque? In fact, I moved to the mosque. Am I obligated to repeat the prayers I prayed behind him? I ask for your guidance?
Answer: It is obligatory for those in the hospital who are able to pray in the mosque to pray in the mosque near the hospital, whether they are a doctor, a nurse, a visitor, or a patient who is able to attend the mosque. It is obligatory for them to pray in the mosque; for Allah, Mighty and Majestic, has prescribed the enlivening of mosques for the establishment of prayer therein, as He, the Exalted, said: [Surat al-Nur: 36].
So the conclusion is that it is obligatory for those in the hospital who are able to reach the mosque to pray in the mosque. In the hadith, it is reported from him (peace and blessings be upon him) that he said: It was narrated by Ibn Majah, al-Daraqutni, and others with a good chain of narration. Also, a blind man asked him: So the Prophet (peace and blessings be upon him) said to him: And he did not permit him to pray in his home, even though he was blind and had no guide to accompany him. In another narration from him: This indicates the obligation of performing the prayers in the mosques. There is no difference between the people of the hospital and others. Those who pray in parts of the hospital have contradicted the Sunnah and left the obligatory.
As for praying behind the doctor who engages in talebearing and causes some harm, his prayer is... valid. Praying behind a sinner is valid. However, it should be that only the best of people lead the people in prayer. The best should be sought for the imamate. It should be that the best of people, the most proficient in recitation, and then the most knowledgeable of the Sunnah, be chosen for the imamate, and so on, as came in the hadith from him (peace and blessings be upon him) that he said: Meaning, in terms of Islam.
So the conclusion is that the best and most excellent should be chosen for the imamate, and one who is known for talebearing or other open sinfulness should not lead the people. Rather, it is obligatory for the responsible parties to replace him and not approve of him, but to seek someone else who is better than him if that is feasible. If the people pray behind him, the prayer is valid; for if his prayer is valid in itself, then the prayer behind him is valid. But it should be that only one who is known for justice and uprightness is approved for the imamate. As for the disbeliever, the prayer behind him is not valid. One who has been ruled to be a disbeliever, the prayer behind him is not valid. This is only in the case of the open sinner who is not a disbeliever. If he does not find an imam better than him, he prays behind him. And if he prays behind him also out of necessity, or because other mosques are far, or similar to that, there is no harm. The point is that the prayer behind him is valid. But if someone who is more deserving and better than him is available, let him pray behind the one who is better and more excellent, as a way out of the disagreement of the scholars who say that the prayer behind the open sinner is not valid. And Ibn 'Umar (may Allah be pleased with them both) prayed behind al-Hajjaj in Hajj, and al-Hajjaj was among the most sinful and most unjust of people. Yes.