"The Messenger of Allah said: 'If anyone of you has intercourse with his wife, then he wants to do it again, let him perform ablution.'" (Using translation from Ibn Mājah 587)
"إذا غَشِى أحدُكُمْ أهْلَه، ثُمَّ أراد أن يعودَ فليتوضَّأ وضُوءَه للصَّلاة".