What is the ruling on a person sponsoring an abandoned child from an orphanage and adding him to his name in official documents?

It is not permissible, according to Islamic law, to attribute a foundling to the one who adopted him as a son and relate him to him. This involves falsehood, deceit, the mixing of lineages, and alteration of inheritances. Allah has forbidden attributing a child to other than his father. Allah Almighty says: "Nor has He made your adopted sons your [true] sons. That is [merely] your saying by your mouths, but Allah says the truth, and He guides to the [right] way. Call them by [the names of] their fathers; it is more just in the sight of Allah. But if you do not know their fathers, then they are your brothers in religion and your protectors." The Prophet, peace and blessings be upon him, said: "Whoever claims to be the son of other than his father, while he knows [that he is not], then Paradise is forbidden for him." This designation must be changed and amended. As for showing kindness to the foundling, raising him, and being good to him, these are well-known deeds that are encouraged in Islamic law.