Is the prayer valid behind an innovator or an open sinner?

Question:
Is the prayer valid behind an innovator or an open sinner?

Answer:
This requires a detailed explanation:
If the innovator is a disbeliever: such as one who calls upon al-Badawi, or calls upon al-Husayn, or others, seeking aid from other than Allah, or calls upon idols, or planets, or stars; one does not pray behind him.
As for an innovator who has an innovation short of associating partners with Allah: an innovation of some of the Sufis, the innovation of the Mawlid, and he does not associate partners with Allah, another innovation in which he is not an associate of partners with Allah; one prays behind him, but someone else is better than him. It should not be that he is the imam; one should seek someone who is better and more excellent than him, but the prayer behind him is valid if his innovation does not take him out of Islam.
And so with the sinner: if his sin does not take him out of Islam: such as one who shaves the beard, or one who lets his garment hang below the ankles; his prayer is valid, but it is not befitting that he be taken as an imam. One should seek an imam other than him who is sound, not one who is openly committing sin. So with one who is known to be undutiful to his parents, or that he consumes intoxicants at times; one prays behind him while he is sane; the prayer is valid, but it is not befitting that he be taken as an imam. This is the correct view.
And some of the scholars of knowledge said: If he is an open sinner, one does not pray behind him, and the prayer behind him is not valid.
And the correct view is that it is valid, but it is not befitting to take him as an imam. Ibn 'Umar and others prayed behind al-Hajjaj ibn Yusuf, and he was among the most unjust of people. And the Prophet (peace and blessings be upon him) said regarding the rulers: , and among the rulers are the bad and the good, among them is the unjust, among them is the open sinner, and among them are others.