GOD WILL BLESS YOU!
“Should people cheat God? Yet you have cheated Me!
“You have cheated Me of the tithes and offerings due to Me. Bring all the tithes (and) “I will open the windows of heaven for you. I will pour out a blessing so great you won’t have enough room to take it in!” Try it! Put Me to the test! Malachi 3:8, 10
This refers to living consistently in the blessing of God, not just a one shot healing.
Healing is a free gift, but we must fulfill the conditions that God sets out including releasing your finances to Him. You have to give to God what is rightly His. You cannot rob from God and expect Him to consistently heal you.
So you say that this biblical reference comes only from the Old Testament. Yet, the New Testament goes even further in the Acts of the Apostle, where Jesus asks a young man to sell everything he had and follow Him.