From Sahih Bukhari (Hadith 2051):
Narrated An-Nu`man bin Bashir:The Prophet (ﷺ) said "Both legal and illegal things are obvious, and in between them are (suspicious) doubtful matters. So whoever forsakes those doubtful things lest he may commit a sin, will definitely avoid what is clearly illegal; and whoever indulges in these (suspicious) doubtful things bravely, is likely to commit what is clearly illegal. Sins are Allah's Hima (i.e. private pasture) and whoever pastures (his sheep) near it, is likely to get in it at any moment
Reference: Bukhari 2051