Deuteronomy 7:15: The Lord will take away from thee all sickness, and will put none of the evil diseases of Egypt, which thou knowest, upon thee.
God was instructing the children of Israel on how they have to strictly follow His statues and ordinances in order for them to be disease free or curse free in future. God makes it very clear to them that they are a holy people and that they have been chosen to be a special people unto Himself than anyone else in the whole world. God was just letting some things sink into their head as to how they can be partakers of God’s promises for themselves.
We cannot take God for granted and do what we want and still expect God to bless us. God wants us to obey Him completely. Partial obedience is disobedience too. There were certain ground rules that God had set for His children to be plaque free and disease free when they would occupy the promised land. Unfortunately, Israel started worshipping foreign gods, put out the one true God out of their lives slowly and steadily. They were attacked and oppressed by other kingdoms almost their entire time in the promised land. The fact of the matter is God does not want us to be losers or be oppressed by the devil. He wants us to enjoy life everyday. For that, He wants us to obey Him and do what He pleases.
No matter what happens around us, God will protect us if we are careful to be adherent to every word He says. This world is not a trouble free place to be in. The scriptures say that in this world we will have tribulations and trials but to be of good cheer because Jesus has overcome the world. Therefore to have a victorious life, listen to the Victor in your life.