The Exalted says:
“Whoever opposes the Messenger after guidance has become clear to him and follows a way other than that of the believers—we shall leave him to the path he has chosen and roast him in Hell.” (al-Nisāʾ 4:115)
There are many other verses to the same effect.
Whatever guidance or practice those people adhere to is, in fact, a path other than that of the believers—indeed, it is the way of the corrupters and of those devoid of knowledge. Even if one were to imagine that a particular practice of theirs lies outside the general prohibition, the ban still applies to its very genus. Hence, shunning the entire genus altogether is the surest means of avoiding the forbidden, whereas drawing near to it is an open invitation to fall into what is prohibited.
The Most High also says:
“We have sent down to you the Book in truth, confirming the Scriptures that came before it and safeguarding them. So judge between them according to what Allah has revealed and do not follow their desires, turning away from the truth that has come to you. For each of you We have appointed a law and a way. Had Allah willed, He could have made you one community; but He wishes to test you in what He has given you. So race one another toward good deeds. To Allah you shall all return, and He will then inform you about the matters on which you differed … Do not follow their desires, and beware lest they tempt you away from even part of what Allah has revealed to you.” (al-Māʾidah 5:48–49)
To imitate them in their customs is itself submission to their whims—or at the very least, it is a prelude to submitting to those whims. Refraining from such imitation helps one avoid that submission and cuts off its root entirely.
Know, then, that Allah’s Book is replete with prohibitions against resembling the disbelieving nations and with accounts of them that serve as lessons for us to avoid what they did—such as His words, after relating what He did to the People of the Book