Musnad Ahmad 602:0

Narrated to us by Yahya ibn Sa’id, from Shu’bah, who said: Narrated to us Qatadah, from Abu al-Maliḥ, from Abu ‘Abd al-Rahman al-Juhani, from the Prophet (ﷺ), who said: "Do not swear by your fathers, nor by your mothers, nor by the idols. And do not swear by Allah except when you are truthful."