Chazal learned from an Arab

 Gra (Kol Eliyahu Rosh HaShanna 26b): “Our sages did not know the meaning of the verse (Tehilim 58:23): Cast your yahava on G d… Raba Bar Bar Channa was carrying a burden and an Arab said : Place your yahava on my camels.” This seems astounding. How is it possible that our sages did not know the meaning of yahava and the Arab did? The explanation is that they had had a doubt concerning bitachon as to whether a person must first act with his intelligence and then have bitachon that G d would provide that which is good for him or whether it is totally unnecessary to rely at all on one’s own deeds and intelligence. They said that of course a person should make intelligent efforts first and also have bitachon. But this understanding seemed to contradict the verse in Tehilim (58:23) which should have said needs instead of yahava. However this was resolved when they saw that an Arab had asked Raba Bar Bar Channa to place his burden on his camel without charge. Normally Raba Bar Bar Channa should have had to pay the Arab to transport his burden. Therefore since the reverse occurred, they concluded that if it is decreed in Heaven then the service is not only free but the service is offered without being requested. Therefore the word yahava - which means something which normally is paid for - is appropriate. Thus one should rely on G d for everything and it will be provided without pay or effort.