Sa'id bin Abi Khyrh سعيد بن أبي خيرة · Commercial Transactions (Kitab Al-Buyu)

I heard Messenger of Allah (ﷺ) say: But between them are certain doubtful things which many people do not recognize. He who guards against doubtful things keeps his religion and his honor blameless, but he who falls into doubtful things falls into what is unlawful.