It is narrated from Sayyiduna Talq bin Ali (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "A woman should not refuse (herself to) her husband, even if she is on the back of a camel saddle."
Hadith Referenceالمعجم الكبير للطبراني / باب الطاء / 8217