Allah, exalted be His praise, says: "There is no sin upon you if you divorce women before you have touched them or fixed a dower for them, and (in that case) give them some provision (mut'ah)." [Surah al-Baqarah: 236]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / Q14332
Sayyiduna Uqbah bin Amir (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) said to a man: "Shall I marry you to such-and-such a woman; are you pleased?" He said: "Yes." And he asked the woman: "Shall I marry you to such-and-such a man; are you pleased?" She too said: "Yes." So their marriage was concluded without a dower and without anything being given. That man had been present at Hudaybiyah, and a share in Khaybar had been set aside for those people. When his death approached, he said: "The Messenger of Allah (peace and blessings be upon him) married me to such-and-such a woman without a dower and without my giving anything, and I make you witnesses that I have given her my share of Khaybar as her dower." So she took that share and sold it for one hundred thousand. The narrator said: The Messenger of Allah (peace and blessings be upon him) said: "The best dower is the one that is easiest."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14332
Muhammad bin Yahya (may Allah have mercy on him) narrates from Abu al-Asbagh (may Allah have mercy on him) that the man consummated the marriage with his wife, but he had not given her a dower or anything at all.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14333