Fiqh-us-Sunnah Volume 1, Purification and Prayer, Fiqh 1.041A.

If a person in a state of post-sex impurity wants to eat, drink or have intercourse again, he should perform ablution.

Said ‘Aishah, “When the Prophet, upon whom be peace, was in a state of impurity because of intercourse and wanted to eat or sleep, he would perform ablution.” ‘Ammar ibn Yasar reported that the Prophet permitted a person in post-sex impurity to eat, drink or sleep if he performed ablution first. (Related by Ahmad and at-Tirmizhi, who classified it as sahih.)

Abu Sa’eed reported that the Prophet, upon whom be peace, said, “If one has intercourse with his wife and wants to repeat the act, he should perform ablution.” (Related by “the group,” except for al-Bukhari. Ibn Khuzaimah, Ibn Hibban and al-Hakim recorded it with the addition, “It makes the return more vivacious.”)