What is the ruling on a man inserting his finger into his wife's anus for foreplay during intercourse?

It is permissible for spouses to enjoy each other's entire bodies, with the exception of two prohibitions: intercourse in the vagina during menstruation, as Allah the Almighty says: "And they ask you about menstruation. Say, 'It is a discomfort.' So keep away from females during menstruation," and one should not touch her between her navel and her knee, according to the hadith of Aisha. The second is anal intercourse with the wife, due to the Prophetic hadith: "Accursed is he who has intercourse with his wife in her anus," and because the anus is a place of permanent impurity, and because this act contradicts sound human nature and may lead to more heinous acts.