Musannaf Ibn Abi Shaybah

It is narrated from Hazrat Muswar bin Zaid (may Allah be pleased with him) that a woman found a child, she raised him and spent on him until he became an adult. Then the woman demanded maintenance from the boy. A letter was written to Hazrat Umar bin Abdul Aziz (may Allah have mercy on him) seeking a ruling on this matter. He replied that the woman should be made to swear an oath that she did not spend on the boy with the intention of seeking reward. If she swears the oath, then the boy should be ordered to strive to provide maintenance for her.

Hazrat Aamir (may Allah have mercy on him) says that if someone spends on a foundling (an abandoned child), then (later) nothing is obligatory upon that child.

Hazrat Ali (may Allah be pleased with him) said: Any found child is free. If the person who raised the child demands maintenance, then if the child (upon growing up) is wealthy, he will return it; and if the child is not wealthy, then whatever that person spent on him is charity.

Hazrat Khalid bin Abi Salat (may Allah have mercy on him) narrates that Hazrat Umar bin Abdul Aziz (may Allah have mercy on him) said to me that Hazrat Umar (may Allah be pleased with him) had given a verdict regarding a child born out of wedlock that he should settle the account of his upbringing with the one who raised him for the service rendered, and whatever remains, he should strive for it himself. And I have given the verdict that he should settle the account for the service rendered, and whatever remains should be paid from the public treasury (Bayt al-Mal).