It is narrated from Sayyiduna Zayd bin Arqam (may Allah be pleased with him); he said: I was sitting with the Prophet (peace and blessings be upon him) when a man from the Jews asked him (peace and blessings be upon him): "Do you claim that in Paradise there will be food, drink and spouses?" The Prophet (peace and blessings be upon him) said: "Yes." The Jew said: "We find it to be pure and fragrant (so how will there be waste?)." The Prophet (peace and blessings be upon him) said to him: "Do you believe in the tree of musk, and do you find it in your Book?" He said: "Yes." He said: "Then urine and janabah (sexual impurity) are sweat that flows like musk from their locks of hair down to their feet."
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4991