I am the Lord your God who heals all your diseases.
Exodus 15:26 (WEB)
and he said, “If you will diligently listen to the voice of Yahweh your God, and will do that which is right in his eyes, and will pay attention to his commandments, and keep all his statutes, I will put none of the diseases on you, which I have put on the Egyptians; for I am Yahweh who heals you.”
This promise takes place at the waters of Marah, where the Israelites came looking to find fresh water to quench their thirst. Instead of finding a place to drink, they found bitter water which caused them to rise up and complain against Moses. In response to Moses' prayer, the Lord showed him a tree to throw into the water. As soon as the tree went into the water, the water became sweet and drinkable.
It is right after this encounter that God makes today's promise to the Israelites. He tells them that if they will only listen to Him and obey His direction, that they will not suffer the diseases that the Egyptians suffered. Our Heavenly Father goes on to declare a promise that is as relevant today as it was back then... "For I am the LORD that healeth thee". (KJV)
Whatever your affliction, whatever your sickness, God can take the bitterness of your experience and make the bitter waters sweet by one single tree, which I believe represents the cross of Christ. The Bible says that Jesus was wounded for our transgressions and bruised for our iniquities and by His stripes we are healed. This is a promise that we can count on...for our God is a God that heals us!