The Vilna Gaon explains a Gemarah in Rosh Hashana (26) as follows: There was a discussion in the Bais Hamedrash regarding the passuk “השלך על ה יהבך והוא יכלכלך ” – “Cast your burden on Hashem and He will sustain you.” The Gemarah says that the Rabanan couldn’t understand the meaning of the word יהבך. The Gr”a explains that they certainly understood the meaning of the word but they were struggling with the concept. They were trying to decide if a person must rely solely on Hashem or if you are meant to do everything in your power to meet your goals and to also rely on Hashem that He will help you along. In the end, they agreed that a person must do as much effort as he can and also rely on Hashem. However, they still had difficulty with the word Yehavecha, the passuk should have used a term like tzirachecha –”your needs.”
One day shortly after, Raba Bar Bar-Chana was traveling with an Arab merchant while carrying a bundle. As they were going, the Arab turned to Raba and told him, “Take your ‘yehavich’ and throw it on my camel [and it will carry it for you].” When Raba Bar Bar-Chana heard the term “yehavich” he understood that Hashem was sending him a message through the words of the Arab. Normally, to have someone carry your packages it comes at a price, but here, the Arab asked him to give over the bundles to carry. The Rabanan then understood that the passuk was teaching that when you rely on Hashem, even if it’s a situation where normally you must ask others for assistance, if Hashem wants you to have it, then it will be taken care of for you. When someone relies on Hashem, he doesn’t need to exert effort, Hashem will do it for him.