I understand that a woman has to be intimate with her husband on his request, but where in the Qur'an does it say this?

This is all proof I could find of the above: One of the rights that the husband has over his wife is that he should be able to enjoy her (physically). If he marries a woman and she is able to have intercourse, she is obliged to submit herself to him according to the contract, if he asks her. That is after he gives her the immediate mahr, and gives her some time ? two or three days, if she asks for that ? to sort herself out, because that is something that she needs, and because that is not too long and is customary. If a wife refuses to respond to her husband?s request for intercourse, she has done something haraam and has committed a major sin, unless she has a valid shar?i excuse such as menses, obligatory fasting, sickness, etc. It was narrated that Abu Hurayrah (may Allaah be pleased with him) said: ?The Messenger of Allaah (peace and blessings of Allaah be upon him) said: ?When a man calls his wife to his bed and she refuses, and he went to sleep angry with her, the angels will curse her until morning.?? (Narrated by al-Bukhaari, 3065; Muslim, 1436)