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 is His slave and Messenger.
Swearing while placing the hand on the Mus-haf is not a practice that is reported from the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, nor from the Companions . It is rather one of the religious innovations introduced by the judges to intensify the gravity of an oath, so that it would deter the wrongdoers more strongly and frighten them more of lying. Al-Hattaab said in his book Mawaahib Al-Jaleel: “As for intensifying the gravity of the oath by asking the swearer to swear while placing the hand on the Mus-haf, it is a religious innovation that is not reported from any of the Companions . However, such a practice is regarded as permissible by the Shaafi‘i scholars of Fiqh.”
That is so as regards asking the person to swear when there are disputes. But if one does it by himself, it will be dealt with like other oaths. If the swearer is truthful, he will incur no sin and nothing is required of him. But if he is lying, his oath will be a Ghamoos Yameen (false oath) which causes the person to incur a lot of sins. There is a difference in opinion among the scholars over the expiation for a Ghamoos Yameen. The majority are of the opinion that its expiation is repentance and seeking forgiveness. The Shaafi‘i scholars, however, view that an oath expiation is due along with repentance and asking for forgiveness.
Allaah Knows best.