He (Ibn Taymiyya) was asked about masturbation; he answered: Now in principle there is a prohibition on masturbation according to the majority of scholars, and those who do it may be given a discretionary punishment [ta'zir], although it is not the same as adultery. But Allah knows best.
He was asked about masturbation – is it prohibited [haram] or not? He answered: Now masturbation with one's hand is prohibited according to the majority of scholars, and this is the most correct of the two viewpoints in the school of Ahmad; accordingly, those who do it may be given ta'zir. In the other viewpoint, it is disliked [makruh] but not prohibited, although most of them do not permit it simply out of fear of distress [‘anat, i.e. adultery] or anything else. It has been transmitted from a group of the Sahaba [Companions] and Tabi'un [Followers] that they allowed it if necessary, such as if one fears adultery (although he is not exempt except in this instance), or if he fears that he will become ill if he does not do it; this is what Ahmad and others say, and except in cases of necessity I do not know of anyone allowing it. But Allah knows best.
He was asked about someone whose body becomes agitated and so he masturbates with his hand, or sometimes he might press his thighs on his penis, knowing that this can be alleviated by fasting, although it is hard on him. The answer: There is no offense regarding any fluid that comes out unintentionally, but he is to bathe [ghusl] whenever fluid comes out forcefully. Having an emission intentionally by masturbating with one's hand is prohibited according to most scholars, and it is one of the two things related from Ahmad; indeed it is the clearest of the two. In another account this is disliked; however if he feels compelled to do it, for example if he fears adultery if he does not masturbate, or fears malaise, scholars have two well-known points of view regarding this. Groups of both early and later scholars [salaf and khalaf] allowed it in such situations, while others forbade it. But Allah knows best.
Issue: Regarding someone who beats his penis with his hand until he ejaculates – what is obliged of him? The answer: Now beating the penis with the hand until one discharges, this is absolutely prohibited according to most legal scholars, although according to a group of the imams, it is prohibited except in necessity, such as if one fears distress or fears malaise or fears adultery; in that case masturbation is more fitting.