Is the testimony of a person regarding the names of heirs whom he does not fully know, while swearing to it, and with his knowledge of the possibility of the existence of other heirs who were not mentioned, considered a false testimony? What is the ruling on the oath he swore, and what is incumbent upon him to expiate for this sin?

Giving testimony is a grave matter in Islam. For this reason, Islam has forbidden false testimony, making it one of the gravest sins, and has urged the giving of truthful testimony, emphasizing the necessity of verifying and confirming it. Based on this, giving testimony in a matter about which one does not have sufficient knowledge is a great error, and an oath sworn upon it is considered a yameen ghamoos (a perjurious oath). This occurs when a person knowingly and intentionally swears a false oath about a past event, or if they are doubtful or have a weak presumption. The majority of scholars hold that no expiation (kaffarah) is required for it. Therefore, whoever has done this must repent for their action. The conditions for repentance are: abstaining from the act, regretting it, and resolving not to return to it. There is no harm in offering expiation as a precaution. The judge must be informed of the uncertainty in the testimony, out of concern that it might have led to the forfeiture of a right for an heir or a legatee.