What is the ruling on offering a gift to someone to encourage them to accomplish a specific task that does not harm others, and is not intended as a bribe?

A forbidden gift is a bribe (Rishwah), which is something given to invalidate a right or to establish a falsehood. The Prophet (peace and blessings be upon him) cursed "the briber and the bribed."

Regarding giving a gift to a worker: - If he is a craftsman working for himself, there is no harm in giving a gift. - If he is an employee or worker for another entity: 1. If he requests the gift, it is a bribe, and you should not give it to him. 2. If he does not request it, but the work is not done except by it, and you are compelled to give it, and it is not to invalidate a right, or establish a falsehood, or to give you preference over others, then there is no sin upon you, and the sin is upon him. 3. If he does not request it, and the work does not depend on it, and your intention is not bribery, then there is no harm in it. However, it is preferable to avoid it to prevent linking the completion of tasks with gifts and to avoid suspicion.