It is not permissible to pray behind an imaam who is a charlatan and liar

 

Is it permissible to pray behind an imaam who is a charlatan and liar, knowing that some of these people can recite Qur’aan very well? Please advise us, may Allaah reward you with good.

Praise be to Allaah. 

If the imaam is a charlatan who claims to have knowledge of the unseen
or who does false and evil actions, then it is not permissible to take
him as an imaam or to pray behind him, because whoever claims to have
knowledge of the unseen is a kaafir – we ask Allaah to keep us safe
and sound. Allaah says (interpretation of the meaning):  

“Say: “None in the heavens and
the earth knows the Ghayb (Unseen) except Allaah” [al-Naml
27:65]  

The same applies to one who practices sihr (witchcraft or magic) –
he comes under the same rulings as the kaafir, because Allaah says (interpretation
of the meaning):  

“They followed
what the Shayaateen (devils) gave out (falsely of the magic) in the
lifetime of Sulaymaan (Solomon). Sulaymaan did not disbelieve, but the
Shayaateen (devils) disbelieved, teaching men magic and such things
that came down at Babylon to the two angels, Haaroot and Maaroot, but
neither of these two (angels) taught anyone (such things) till they
had said, ‘We are for trial, so disbelieve not (by learning this magic
from us)’…”

[al-Baqarah 2:102]  

But if he is a person who commits some sins, but he does not do any
actions of kufr such as practising witchcraft and claiming to have knowledge
of the unseen, then prayers offered behind him are valid, but it is
better to find someone else who is of sound character and is righteous,
to be on the safe side and to avoid differing with those scholars who
say that it is not permissible to pray behind (such a person). 

Sinners should not be taken as imaams, but if they are already in
that position, prayers offered behind them are valid, because it may
be that the people are being tested by means of them, or necessity may
force us to pray behind them. But in the case of one who calls upon
anyone other than Allaah, or who seeks the help of the dead, we should
not pray behind him, because this action makes him one of the kuffaar,
for this is the action of the mushrikeen whom the Prophet
(peace and blessings of Allaah be upon him) fought against in Makkah
and elsewhere. We ask Allaah to reform the Muslims and to grant them
understanding of His religion, and to cause the best of them to become
their leaders, for He is the All-Hearing, Ever ready to respond.