“For all the promises of God find their Yes in him. That is why it is through him that we utter our Amen to God for his glory,” (2 Corinthians 1:20).
Commenting on this verse, John Calvin writes,
“The promises, I say, are testimonies of Divine grace: for although God shows kindness even to the unworthy, (Luke vi. 35,) yet when promises are given in addition to his acts of kindness, there is a special reason- that in them he declares himself to be a Father. Secondly, we are not qualified for enjoying the promises of God, unless we have received the remission of our sins, which we obtain through Christ.
Thirdly, the promise, by which God adopts us to himself as his sons, holds the first place among them all (emphasis mine). Now the cause and root of adoption is Christ; because God is not a Father to any that are not members and brethren of his only-begotten Son.
Everything, however, flows out from this source- that, while we are without Christ, we are hated by God rather than favourably regarded, while at the same time God promises us everything that he does promise, because He loves us. Hence it is not to be wondered if Paul here teaches, that all the promises of God are ratified and confirmed in Christ,” (Calvin’s Commentaries, vol. XX, “2 Corinthians,” pp. 137-138).