Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, states: “Islam teaches us that we are to exercise the duty of nasihah (sincere advice) towards others. Nasihah is to wish good for others as we wish good for ourselves. The Prophet (peace and blessings be upon him) said, “No one can be a true believer until he loves for his brother what he loves for himself.” He also said, “Religion is sincerity.” When the Companions asked, “Towards whom, Messenger of Allah?” he replied, “Towards Allah, His Book, His Messenger, leaders and all people.”
In Islam, we cannot recommend anyone in any matter unless we know the person sufficiently enough to ascertain their integrity of character. This requires close familiarity with the person as a neighbour, as a business partner, or as a companion on a long journey, et cetera, where we have lots of opportunities to test the true nature of the person.

Therefore, if a muslim doesn’t know someone well, and in spite of that they still recommended the person, then you have clearly breached a fundamental principle. Such person has simply betrayed the trust of Islamic brotherhood and have failed to look after their interests by agreeing to his request or suggestion. Hence, this muslim is partially responsible in the sight of Allah.