Is the delivery person who does not inform customers of the reliability of the products he delivers, despite knowing some of their flaws, sinful on the grounds that his job is limited to delivery?

When a brother seeks advice from him, it is incumbent upon him to offer it, for the Messenger of Allah, peace and blessings be upon him, said: "If he seeks your advice, then advise him." Scholars have differed regarding the obligation of advice: is it a collective obligation (fard kifayah) or an individual obligation (fard ayn)?

Some scholars hold that it is a collective obligation (fard kifayah), meaning it is discharged for the rest if some undertake it. It is obligatory within one's capacity, provided one believes it will be accepted and is safe from harm.

Others hold that it is an individual obligation (fard ayn) upon a Muslim, whether requested or not, if one believes it will be beneficial and is safe from harm. However, if one fears harm, then they are at liberty not to offer it.

Accordingly, it is incumbent upon the advisor to disclose any flaw or defect he knows of, especially if advice is sought from him. He is not permitted to conceal it, unless he fears harm or injury from giving the advice.