Is ablution (wudu') required between each instance of intercourse during the same sexual encounter?

It is recommended for a person who has had intercourse with his wife and then wishes to have intercourse again to perform ablution between the two acts, based on the Prophet's (peace and blessings be upon him) saying: "If one of you comes to his wife and then wishes to return, let him perform ablution between them, for it is more invigorating for the return." This ablution is recommended according to the majority of scholars. The Dhaahiris, however, differed, saying it is obligatory. The correct view is that it is for recommendation, because the rationale provided, "for it is more invigorating for the return," shifts the command from obligation to guidance.