What is the ruling on marrying an abandoned child?

If both prospective spouses are free of impediments to marriage, then there is no objection for an orphan of unknown parentage to marry the woman he wishes to marry, especially if he is a person of good character and religious commitment. This is based on the Prophet's (peace and blessings be upon him) saying: "If someone whose religious commitment and character you approve of proposes to your daughter, then marry her to him. If you do not do so, there will be tribulation on earth and widespread corruption."