The worshippers in his mosque do innovations and wrong actions – how should he advise them?

Firstly: 

You have done well to ask before doing something that may
have a negative impact on those worshippers, and may also backfire on you,
in your prayer in particular and in your life in general. 

Among the most important attributes of the one who calls
people to Allaah are: knowledge and wisdom, with which the daa’iyah can
achieve that which many others fail to achieve who lack the blessing of
knowledge or wisdom and the skill to deal properly with those who differ in
some way. 

Wisdom does not mean being lenient or forsaking any aspect of
the truth, rather it means adopting the appropriate approach so that one may
succeed in leading people from ignorance and innovation to knowledge and the
Sunnah.  

The wise daa’iyah knows that these worshippers refer for
their fatwas to imams and scholars whose religious commitment and knowledge
they trust, so how can he want them to turn away from them and turn directly
to him without paving the way? 

The one who wants to call people to Islam should know that
surprising people with the Sunnah of which they are unaware and denouncing
them for what they are doing may cause them to hate the Sunnah and those who
follow it, and this is what creates barriers between the daa’iyahs and some
of the people when they try to teach them and explain the Sunnah to them.
This does not mean that he should stop trying to advise them, rather it
means that he should adopt a gradual approach in calling them. 

Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allaah have
mercy on him) said, explaining the words of ‘Ali ibn Abi Taalib, “Talk to
the people about what they appreciate and accept; do you want them to reject
Allaah and His Messenger?’ (narrated by al-Bukhaari) as follows: 

The words in the report of ‘Ali (may Allaah be pleased with
him), “Talk to the people” means when preaching and otherwise. “What they
appreciate and accept” means, what they may understand, so that they will
not be confused. Hence it was narrated that Ibn Mas’ood (may Allaah be
pleased with him) said: “You will never tell a people anything that they do
not understand but it will be a cause of confusion for some of them.”
Narrated by al-Bukhaari.  

Hence it is wise when calling people to Islam not to
overwhelm the people with things that they cannot understand, rather one
should call them gradually, so that they may gradually comprehend what you
are telling them.  

The phrase “do you want them to reject Allaah and His
Messenger?” means: If you tell the people things that they do not
appreciate, do you want them to reject Allaah and His Messenger? Because if
you say “Allaah said such and such and His Messenger said such and such,”
they will say, This is a lie, if it is beyond their comprehension, and in
that case they will not be disbelieving Allaah and His Messenger, rather
they will be disbelieving you and the words you attribute to Allaah and His
Messenger, thus they will be ultimately disbelieving Allaah and His
Messenger, not directly but via the one who told them that.  

 If it is said: Should we forego speaking of that which
people do not understand even though they are in need of that? My answer is:
We should not forego that, but we should tell them in a way that is
acceptable to them, by telling them gradually, until they accept this idea
and feel at ease with it, and we should not ignore that which they cannot
understand and say that this is something objectionable so we should not
speak of it. 

For example: Following the Sunnah which the people are not
used to and find objectionable. We should follow it, but after we tell them
of it, until their hearts accept it and feel at ease with it. 

It may be understood from this report the importance of
wisdom in calling people to Allaah, may He be glorified and exalted, and
that the daa’iyah must have insight into the mentality of the people he is
calling, and use a different approach for each individual. 

Majmoo’ Fataawa al-Shaykh al-‘Uthaymeen
(10/774, 775). 

So you have to follow the path of wisdom in calling these
people to give up communal dhikr and the other innovations that they do, and
to follow the Sunnahs that they are ignoring. We think that you should do
the following: 

1 – Continue to lead them in prayer as an imam, and seek to
draw closer to their hearts by leading the prayers, and do not leave it for
someone else to take charge of their prayer and ‘aqeedah. 

2 – Do not join them in their dhikr and other innovations,
but remember that it is essential for you to remain in the place where you
prayed so that you may recite the prescribed dhikrs by yourself. 

3 – Give them daily lessons that take up only a little time,
as this may be a way of stopping their innovations as well as calling them
and teaching them. 

4 – Focus on the importance of the Sunnah and of following
proper evidence, and mentioning the examples of the Sahaabah, Taabi’een and
prominent imams, especially those whom you see that they love and respect. 

5 – Do not object to their innovations directly, and do not
criticize the contemporary imams and scholars whose opinions they follow. 

6 – Pay attention to the leaders and knowledgeable ones among
them who have an influence on them, and try harder with them than with
others. 

7 – Give them gifts occasionally, such as books, tapes and
pamphlets, whilst also honouring them by offering food and drink as much as
you can. 

8 – Join them on permissible occasions, and try to draw close
to them by having a good attitude towards them. 

This does not apply to you alone, rather it applies to every
daa’iyah who wants to succeed in a community where there is a great deal of
innovation and where the people do not respect or follow the Sunnah a great
deal.  

Do not forget to seek the help of Allaah in your du’aa’, and
be sincere in doing it, seeking thereby the countenance of Allaah. You
should focus on the idea that these people are sick and need the remedy that
you possess, but they do not realize that they are sick, so how can you
deliver the remedy to them in a wise manner? 

And Allaah knows best.