Shaykh al-Islam Ibn Taymiyah was asked about a man who claimed to be a holy man, then he saw a snake and some of the people wanted to kill it, but he stopped them, then he picked up the snake trying to do a miraculous deed, but the snake bit him and he died. Is it permissible to offer the funeral prayer for him or not? 

He replied: 

Praise be to Allaah, the Lord of the Worlds. The scholars and people who are religiously committed should not pray for this man and others like him, but the ordinary people should pray for him, just as the Prophet (peace and blessings of Allaah be upon him) refrained from praying for a man who had committed suicide, and one who had stolen from the war-booty, but he said: “Pray for your companion.” They said to Samurah ibn Jundub: “Your son did not sleep last night.” He said, “Was it because he ate too much?” They said: “Yes.” He said: “If he had died I would not have prayed for him.” Samurah explained that if he died because he had eaten too much, he would not pray for him, because he would have killed himself by eating too much. And it is more appropriate that the scholars and those who are religiously-committed should refrain from offering the funeral prayer for this man who prevented others from killing the snake, and held it in his hand until it killed him, because he killed himself. 

Al-Fataawa al-Kubra, 3/20, 21