Is the giver of charity considered sinful if the beneficiary dies days after receiving the charity, and what should he do if that is the case?

The agent must perform the entrusted task to the fullest, for agency is a trust. If the principal instructs you to pay only 100 dinars out of an original 100 euros, and you have 50 dinars remaining, you must return them to the principal or ask him how to dispose of them. If he authorizes you to pay them to the heirs of the deceased person who was intended to receive them, then there is no blame or liability upon you.