There is an Islamic group working in the field of Da'wah and its members are simple ordinary people. Their activities include delivering sermons in mosques, however, their language is poor and they do not distinguish between Saheeh and Dha'eef narrations. Moreover, sometimes they cause unrest among the people in the mosque. What is your opinion?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and messenger.

Unquestionably, teaching the Quran and Sunnah and calling people to adhere to virtue is greatly rewarded by Allaah The Almighty.  Muslims must train people to assume such a noble task, which Allaah has made obligatory on them.  Allaah Said (what means): 

*     {And let there be [arising] from you a nation inviting to [all that is] good, enjoining what is right and forbidding what is wrong, and those will be the successful.}[Quran 3:104]

*     {Say, "This is my way; I invite to Allaah with insight, I and those who follow me. And Exalted is Allaah; and I am not of those who associate others with Him."}[Quran 12:108] 

The Messenger of Allaah, sallallaahu ‘alayhi wa sallam, commanded us to convey even a single verse from him. [Al-Bukhari] He  also instructed anyone who knows anything said by the Prophet to convey it to others. [Al-Bukhari and Muslim]

The Prophet, sallallaahu ‘alayhi wa sallam, also stated that Allaah The Almighty, His angels, the inhabitants of the skies and the earth, and even the ant in its nest and the whale in the sea will pray for the one who teaches people goodness and religion. [At-Tirmithi]

Hence, it becomes clear that working in the field of Da'wah and teaching people the ways of piety are great acts of worship.   At the same time, anyone who assumes this noble task should be fully acquainted with what he is calling for, because an ignorant person can never teach others. 

Consequently, whoever wants to deliver lessons should first make sure that he only intends to please Allaah The Almighty by doing this work. He should then choose the subjects that benefit people.  With regard to the content, he should verify the narrations and sayings that he will quote.  In so doing, he would benefit himself as well as his audience. 

However, causing unrest and creating dispute and disagreement among Muslims are prohibited and Allaah The Almighty warned us against that in the Quran as did the Prophet, sallallaahu ‘alayhi wa sallam, in the Sunnah.

In brief, any person or group who tries to call people to Islam and teach it to others with wisdom and good instruction, spreads the Sunnah and educates the Muslims in conformity with the methodology of the righteous predecessors, their work and efforts are good, acceptable and rewarded by Allaah The Exalted.