What is the ruling on a husband having anal sex with his wife if both spouses agree to it?

It is forbidden for spouses to agree on engaging in the prohibited act (anal intercourse), and this is considered cooperation in sin and aggression. Rather, it is obligatory for them to abstain from it. If one of them requests it from the other, the latter must advise them and remind them of the prohibition of this act and the curse that results from it, based on the Prophet's (peace and blessings be upon him) saying: "Cursed is he who has intercourse with his wife in her anus." Imam Ibn Taymiyyah mentioned that both of them should be disciplined (by the authorities), and if they do not desist, they should be separated.