Is not wearing a shirt considered a weakness in faith, as some claim?

A Muslim must cover his 'awrah with something that does not reveal it. A thobe is preferred because it is more concealing, and it was the garment most beloved to the Prophet, peace and blessings be upon him. It is permissible to wear trousers if they are loose-fitting, cover what is between the navel and the knee, and are not transparent. Wearing trousers is not considered imitation of non-believers due to their widespread use among Muslims and the fact that they are no longer exclusive to non-believers. The prohibition against imitation ceases when the exclusivity of non-believers over something disappears.

Therefore, it is not permissible to accuse someone who wears trousers – within the aforementioned guidelines – of weak faith, even though wearing a thobe is more preferable.