Learning Torah is a guten zach

Question ? Why do we give tzedakah to someone going to Israel
Answer Because we make him a sliach mitzvah guy and they are protected from harm !
Then ponder-- Isnt he a sliach mitzvah guy all by himself with out my tzedakah ? He is going to Israel- that is a MItzvah. Ah you may say it is different if he is doing the mitzvah himself or is being a sliach for someone else- But I saw the source for the protection is from the fact that a person going to Yerusalyim on Regalim doesnt have to be afraid that something bad may happen to his property in his absence since he is away on a mitzvah and this was brought as the source of a sliach mitzvah is protected from harm. Im confused. The navi Shumuel was told by Hashem to go to David and annoit him king- He says he is afraid of King Saul and Hashem has to create a trick that Shumel is really only going to David for sacrifices- Shumeul is a sliach mitzvah guy of Hashem and he is afraid of harm!- This was answered by the fact that the protection from harm is only when it is not in a place that is common for harm and crossing King Saul wouldnt commonly cause harm