Under the old covenant, physical healing was included in Israel’s covenant with God. Just a few days after the Exodus, God made Israel this promise:
If you will give earnest heed to the voice of the Lord your God, and do what is right in His sight, and give ear 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, the Lord, am your healer (Ex. 15:26).
Anyone who is honest will have to agree that healing was included in Israel’s covenant with God, contingent upon the people’s obedience. (Incidentally, Paul makes it clear in 1 Corinthians 11:27-31 that physical health under the new covenant is also contingent upon our obedience.)
God also promised the Israelites:
But you shall serve the Lord your God, and He will bless your bread and your water; and I will remove sickness from your midst . There shall be no one miscarrying or barren in your land; I will fulfill the number of your days (Ex. 23:25-26, emphasis added).
You shall be blessed above all peoples; there will be no male or female barren among you or among your cattle. The Lord will remove from you all sickness; and He will not put on you any of the harmful diseases of Egypt which you have known, but He will lay them on all who hate you (Deut. 7:14-15, emphasis added).
If physical healing was included in the old covenant, one would wonder how it could not be included in the new covenant, if in fact the new covenant is better than the old, as Scripture states:
But now He [Jesus] has obtained a more excellent ministry, by as much as He is also the mediator of a better covenant, which has been enacted on better promises (Heb. 8:6, emphasis added).
