Muhammad bin Abi 'Adi محمد بن أبي عدي · The Book of Oaths and Vows

"The oath by which the Messenger of Allah used to swear was: 'No, by the Controller of the hearts.'"

"The Messenger of Allah said: 'Whoever swears by a religion other than Islam, telling a lie, will be as he said.'" In his narration, Qutaibah said: "Intentionally." Yazid said: "Telling a lie will be as he said, and whoever kills himself with something. Allah will punish him with it in the Fire of Hell."