A question was put to the marja`:
What is the ruling on full adoption, which is adopting a child and giving him or her the last name of the parents and attributing the child to their lineage?
The marja`, Imam Muhammad Sa`id Ramadan Al-Bouti (d. 1434 AH), may Allah be pleased with him, gave the following reply:
Full adoption, i.e. adopting a child and giving him or her the last name of the parents and attributing the child to their lineage is from the ways of the Age of Ignorance which the Revealed Law came to eliminate with a clear, explicit and decisive text in the Book of Allah, Mighty and Majestic,
He has not made your adopted sons to be as your own sons. This is only a word that comes out of your mouths. But Allah speaks the truth and He shows the Right Way. Call these children by their fathers’ names: that is more just in the Sight of Allah.
But if you do not know the names of their fathers, then call them your brothers in faith or your freed or cliented ones. There is no blame upon you if you make a mistake in that regard. What is accounted is the intention in your hearts and Allah is Forgiving, Compassionate.
The wisdom in Allah nullifying this practice from the Age of Ignorance with this clear and decisive text is that full adoption is a form of oppression due to the inheritance being impacted and that this incites the hearts of people towards tribulations.
This in turn also leads to the means of perversions and the corruption of the creation. The child that is fully adopted mixes with the adopted family with the claim that he is one of their own children and both sides – the adoptee and the adopted – fall into slippery affairs.
These affairs are such that there is often no protector of the actual lineage against sexual desires although Allah, the Exalted, has already put into place safeguards. Allah! There are only a few cases that are free from such enormities and where people have controlled themselves.
Indeed in the case of partial adoption, such a matter is permitted. There is no prohibition in one of us accepting a child that was abandoned or that we found or a child that came out of poverty or being an orphan, then we raised the child and spent on it without claiming that child as from our own lineage.
If someone should undertake this type of adoption, then this is a righteous deed and something laudable and deserving of reward.
 Surat ul-Ahzab (33), ayat 4-5
 Translator’s note: The Imam here is referring to the case where parents fall in love with children or vice versa. As the parents have already claimed them as their actual children (even though they are not), this simulates incest. This form of adoption also leads to inheritance being claimed by adopted children when they have no right to it. This one action then goes on to incite enmity between the actual children and their family and the assumed family, with intrigues and false paperwork often brought about based on the one simple lie from the start.
 Ma` An-Nas: Mashurat wa Fatawa, vol.1, pp. 87-88