وَمَنْ تَشَبَّهَ بِقَوْمٍ فَهُوَ مِنْهُمْ
Whoever deliberately resembles a people is counted among them.
Source: أبو داود
تَشَبَّهَ is a Form V past-tense verb, meaning to imitate or deliberately resemble. The phrase بِقَوْمٍ gives the group being imitated, and فَهُوَ مِنْهُمْ is the response to the condition. In that clause, هُوَ is the subject and مِنْهُمْ conveys belonging to them.
Whom a person consciously chooses as a model can shape habits and identity. This brief report should not be treated as a blanket ruling on every shared language, useful technology, or ordinary cultural practice. The introductory lesson is to recognize intentional identification and the influence of conduct and values.