Malachi 3:6:

For I am the LORD, I change not; therefore ye sons of Jacob are not consumed.

Notes on Malachi 3:6:

This is confirmed by James 1:17 in the New Testament.  We also know from Hebrews 13:8 and Hebrews 1:12 that Jesus doesn’t change either.

See also:

Notes on Exodus 15:25-26
Notes on Psalm 107:17-20
Notes on Hebrews 13:8
Notes on James 1:17
The Baseball Diamond of Healing
Jesus the Healer Has Never Changed
How to See God’s Will Concerning Healing
What If You Sin?
To What Extent Can We Claim Old Testament Healing Promises?
Objection: Healing and Miracles Are Not for This Current Dispensation
Objection: God’s Healing Covenant in the Law of Moses Was Only for the Jews
Objection: We Cannot Demand Healing from God Because God Is Sovereign
Objection: If God Wanted Us to Enjoy Perfect Health NOW, He Would Have Already Given Us Immortal Bodies
Objection: God Does Great Miracles Only During Crucial Times in History
Objection: Mental Illness Is Treatable but Not Curable
Objection: Like Any Loving Parent, God Sometimes Has to Tell His Children NO for Their Own Good
Objection: Sometimes God Says, “Yes,” Sometimes He Says, “No,” and Sometimes He Says, “Wait” When You Ask for Healing
Objection: Any Other Objection Not Specifically Covered in This Book