Praise be to Allah.
Shaykh Muhammad ibn ‘Uthaymeen (may Allaah have mercy on him) said: The actions of the enemies of Allaah and our enemies, the kuffaar, fall into three categories:
1 – Acts of worship
2 – Customs
3 – Manufacturing and work
With regard to acts of worship, it is well known that it is not permissible for any Muslim to imitate them in their acts of worship. Whoever imitates them in their acts of worship puts himself at great risk and that may lead to him becoming a kaafir who is beyond the pale of Islam.
With regard to customs such as dress etc., it is haraam to imitate them because the Prophet (peace and blessings of Allaah be upon him) said: “Whoever imitates a people is one of them.”
With regard to manufacturing and professions: in the case of those which serve a general interest, there is nothing wrong with us learning from what they do and benefitting from it. This does not come under the heading of imitating them, rather it is a kind of sharing in beneficial actions and the one who does that is not regarded as imitating them.
With regard to the questioner’s saying, “Does the concept of masaalih mursalah [things that serve the general interests of the Muslims] come under this heading?” we say that masaalih mursalah should not be taken into consideration on its own, rather we say that if we are certain that a particular matter comes under the heading of these things that serve the general interests of the Muslims [masaalih mursalah], then there should be shar’i evidence to that effect, and thus it is part of sharee’ah.
But if sharee’ah proves that this matter is not acceptable, then is does not come under the category of masaalih mursalah, even if the one who accepts it claims that it does.
If it is neither one nor the other, then we should refer to the basic principle. If they are acts of worship, then the basic principle is that acts of worship are forbidden; if they are not acts of worship then the basic principle is that they are permissible. Thus it is clear that this concept of masaalih mursalah cannot be taken into consideration on its own.