Sayyiduna Nu'man bin Bashir (may Allah be pleased with them both) said, and (the narrator said:) by Allah, I will never hear anyone after him say it: I heard the Messenger of Allah (peace and blessings be upon him) say: "The lawful is clear and the unlawful is clear, and what is between them is doubtful." And sometimes he said: "doubtful matters. I will soon give you an example: Allah, the Lord of Might, has set up a protected pasture, and Allah's protected pasture is what He has made unlawful; and whoever grazes (his animals) around the protected pasture is close to entering the pasture." The narrator said: Sometimes he said: "is close to grazing in it; and whoever gets involved in what is doubtful is close to becoming bold." The narrator said: I do not know whether this is part of the hadith or something that al-Sha'bi said.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب البيوع / 10816