What is the ruling on a man lengthening his hair beyond his shoulders, or to his shoulders, if he does not intend to imitate disbelievers or seek fame, but it is rarely done by men in his country, or is done only by the lowest class of people?

It is permissible, in principle, for a man to grow his hair long. However, this is subject to the custom of the society. If the custom is that only effeminate men or transgressors grow their hair long, then it is not advisable to do so, because it involves imitating them. Imitating transgressors is blameworthy in Islamic law, due to the Prophet's (peace be upon him) saying: "Whoever imitates a people is one of them."