What is the ruling on requesting money from an unknown person as a gift, without need or exchange, with the intention of saving it, especially since the one requesting it believed it to be permissible, and is it obligatory to return the money to its owner if he has forgiven it, or if the owner cannot be found?

It is not permissible to beg from people if one is self-sufficient or able to earn a living. And whoever does so for the purpose of hoarding is even more blameworthy, based on the Prophet's (peace be upon him) saying: "Whoever begs from people to increase his wealth is only asking for live coals; let him ask for little or for much." As for one who begs without lying and is given out of the donor's good will, he is not obligated to return it, though returning it is better. The Prophet (peace be upon him) said to Hakim ibn Hizam: "Indeed, this wealth is appealing and sweet. Whoever takes it with a good heart will be blessed in it, but whoever takes it with avarice will not be blessed in it, and will be like one who eats but is never satisfied. And the upper hand is better than the lower hand." The "good heart" here refers either to the recipient (meaning he took it without asking) or to the giver (meaning he gave it willingly).