Sahih Bukhari: Hadith 4943

The same ,Hadith above: A man called Khidam married a daughter of his (to somebody) against her consent. 'If you fear that you shall not be able to deal justly with the orphan girls then marry (other) women of your choice.' (4:3) And if somebody says to the guardian (of a woman), "Marry me to soand- so," and the guardian remained silent or said to him, "What have you got?" And the other said, "I have so much and so much (Mahr)," or kept quiet, and then the guardian said, "I have married her to you," then the marriage is valid (legal). This narration was told by Sahl on the authority of the Prophet.