Is it permissible for a Muslim to retain their non-Islamic name, acquired through adoption and citizenship, if there is a temporary benefit for work, provided that this name is not used among their Muslim acquaintances?

The individual's action of allowing himself to be adopted by a family and changing his name to that of an unbeliever is a grave error, due to the corrupting effects of adoption, such as the mixing of lineages and the forfeiture of rights. Islam has invalidated adoption, as Allah Almighty says: ﴿Call them by [the names of] their fathers; it is more just in the sight of Allah.﴾ (Quran 33:5). Furthermore, changing an Islamic name involves imitating non-Muslims, and the Prophet, peace and blessings be upon him, said: "Whoever imitates a people is one of them." The individual must undo the manifestations of this adoption and rectify the name. If this is not possible in official documents, there is no harm in changing it in personal dealings.