Is there sin upon one who swore an oath by placing his hand on the Qur’an that he would not leave a girl, then left her to avoid what is forbidden (haram)?

Whoever swears by the Mus'haf is like one who swears by Allah, because the Qur'an is the Word of Allah and an attribute of His attributes. If the relationship with the girl is impermissible, then it is obligatory to leave her, break the oath, and expiate for it. The Prophet, peace and blessings be upon him, said: "Whoever vows to obey Allah, let him obey Him; and whoever vows to disobey Allah, let him not disobey Him," and "There is no vow in disobedience to Allah."