On the authority of Abu 'Abdullah al-Nu'man bin Bashir, radiyallahu 'anhu, who said: I heard the Messenger of Allah, sallallahu 'alayhi wasallam, say:
"Truly, what is lawful is evident, and what is unlawful is evident, and in between the two are matters which are doubtful which many people do not know. He who guards against doubtful things keeps his religion and honour blameless, and he who indulges in doubtful things indulges in fact in unlawful things, just as a shepherd who pastures his flock round a preserve will soon pasture them in it. Beware, every king has a preserve, and the things Allah has declared unlawful are His preserves. Beware, in the body there is a flesh; if it is sound, the whole body is sound, and if it is corrupt, the whole body is corrupt, and behold, it is the heart."
[Al-Bukhari & Muslim]
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I think the above hadith makes very clear about doubtful things. May Allah Swt Guide Us. Ameen.
This hadith should not be taken into account with the exclusion of others (including one which suggests that where there is doubt, there is mercy) as otherwise you go down the rabbit hole where increasingly more and more things are put into doubtful by clueless people and eventually even breathing will be considered "better to avoid".
"For too long, we have been a passively tolerant society, saying to our citizens 'as long as you obey the law, we will leave you alone'" - David Cameron, UK Prime Minister. 13 May 2015.