He reported God’s Messenger as saying, “God forbids you to swear by your fathers. If anyone swears he must swear by God, or keep silent.” (Bukhari and Muslim.)
The Prohibition of Swearing by Other Than God
This hadith from Sahih al-Bukhari and Sahih Muslim establishes a fundamental principle regarding oaths. The Prophet Muhammad (peace be upon him) explicitly forbids swearing by one's fathers or any created being. This prohibition stems from the Islamic doctrine of Tawhid (Divine Oneness), where ultimate reverence and oath-taking are reserved for God alone.
Scholarly Commentary from Mishkat al-Masabih
As explained in "Mishkat al-Masabih" (Reference: Mishkat al-Masabih 3407) in the book "Oaths and Vows", classical scholars emphasize that swearing by created beings constitutes a form of shirk (associating partners with God) in reverence. When one swears by their father, they attribute to a created being the sanctity that belongs exclusively to the Creator.
The command to "swear by God or keep silent" provides the lawful alternative. An oath is only Islamically valid when taken in God's name using one of His divine attributes. If one cannot truthfully swear by God regarding a matter, the pious alternative is silence rather than invoking created beings.
Legal and Spiritual Implications
Scholars note this prohibition extends beyond fathers to include swearing by prophets, angels, saints, or any created entity. Such oaths are considered invalid and sinful, though they do not carry the legal consequences of broken oaths sworn by God.
The wisdom behind this teaching preserves pure monotheism in speech and action. It trains the believer to constantly remember God in all affairs and prevents the elevation of created beings to a status of divine reverence.