Assurance comes from faith and faith comes from the word of God. A mystery is something that we do not understand. Spiritual truths are mysteries to all men until God chooses to reveal light into an individual s soul. The Bible is God s mystery to those who do not understand it. But when God reveals His truths to us and we believe, then there is assurance.
Assurance means comfort, and comfort means joy, peace, and love.
There are those, for example, who think that they can lose their salvation. There is certainly no comfort in a promise that is not certain. Yet, if such people would merely believe the promises of God, then they would not have such doubts. Faith in God will give comfort to the heart of man. Verse 2 ended by speaking of God, and of the Father, and of Christ.