Is the one who gives charity obligated to investigate carefully when giving charity, and is he sinful if he places the money in the wrong place, meaning to someone who does not deserve it?

The giver of charity must investigate thoroughly when giving out their charity, especially the obligatory Zakat, so that it does not fall into the hands of those who do not deserve it. If it does fall into the hands of someone undeserving, it will not be sufficient. As for voluntary charity, there is no sin upon the giver if they investigated its recipients and it then fell into the hands of someone undeserving; rather, they will be rewarded. Indeed, Al-Nawawi mentioned a hadith from the Prophet, peace and blessings be upon him, that a man's charity fell into the hands of a harlot, a rich man, and a thief, and his charity was accepted, and it was hoped that each of them would become chaste because of it.