One day, Alexander the Great decided to take a bath! He was overheated, and he wanted to cool off. The river which he decided to use was called Cydnus, and was so cold that when he entered the water, he got a cramp and almost drowned, but was saved by his servants.
Because of the swim, Alexander got sick and was slowly dying. His physician and childhood friend, Philip, was concocting a remedy for his sickness, when Alexander received a letter. On the letter was written that Philip had been bribed by the Persians, and that he was going to poison him. Alexander gave his friend the letter and drank the serum, thus getting healed.
This shows us that Alexander trusted his friends and in return, his friends helped him.