It is narrated from Sayyiduna Atiyyah al-Sa'di (may Allah be pleased with him) - and he was one of the Companions of the Prophet (peace and blessings be upon him) - that the Messenger of Allah (peace and blessings be upon him) said: "The servant cannot be counted among the God-fearing (muttaqin) until he leaves even that in which there is no harm, out of caution against that in which there is harm."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14518