and put His Spirit in our hearts
The phrase "and put His Spirit in our hearts" speaks to the intimate and transformative work of the Holy Spirit within believers. The Greek word for "Spirit" is "pneuma," which can also mean breath or wind, symbolizing life and power. The indwelling of the Holy Spirit is a fulfillment of the promise of the New Covenant, where God writes His laws on the hearts of His people (Jeremiah 31:33). This indwelling presence is not just a passive residence but an active influence, guiding, teaching, and empowering believers to live according to God's will. It is a profound expression of God's love and commitment to His people, ensuring that they are never alone and always equipped for the journey of faith.

as a deposit
The term "as a deposit" is translated from the Greek word "arrabōn," which refers to a pledge or down payment. In the context of ancient commerce, it was a guarantee that the full amount would be paid. Spiritually, this deposit is the Holy Spirit, given to believers as a foretaste and assurance of the eternal inheritance that awaits them. It signifies that what believers experience now in part, they will one day experience in full. This concept of a deposit underscores the certainty and reliability of God's promises, offering believers hope and confidence in the future fulfillment of God's redemptive plan.

guaranteeing what is to come
The phrase "guaranteeing what is to come" highlights the assurance and certainty of God's promises. The Greek word "bebaioō" means to confirm or establish. This guarantee is not based on human effort or merit but on the faithfulness and integrity of God Himself. It points to the eschatological hope that believers have in Christ—the promise of eternal life, resurrection, and the full realization of God's kingdom. This assurance is a source of comfort and encouragement, motivating believers to persevere in faith and live with an eternal perspective, knowing that their future is secure in Christ.

And given the earnest of the Spirit.--Better, for the same reason as before, gave. The Greek word for "earnest" (arrhabon), which occurs here for the first time, and is used only by St. Paul in the New Testament (2Corinthians 5:5; Ephesians 1:14), has a somewhat interesting history. Originally a Hebrew word, from a verb meaning "to mix," "to change," "to pledge," and so used, as a cognate noun, with the last of the three senses, it appears simply transliterated in the LXX. of Genesis 38:17-18. It would seem to have been in common use among the Canaanite or Phoenician traders, and was carried by them to Greece, to Carthage, to Alexandria, and to Rome. It was used by the Greek orator Isaeus, and by Plautus and Terence among the earlier Latin writers. The full form came to be considered somehow as pedantic or vulgar, and was superseded in Roman law by the shortened "arrha," the payment of a small sum given on the completion of a bargain as a pledge that the payer would fulfil the contract; and it has passed into Italian as "arra;" into modern French, as "les arrhes;" into popular Scotch even, as "arles." As applied by St. Paul, it had the force of a condensed parable, such as the people of commercial cities like Corinth and Ephesus would readily understand. They were not to think that their past spiritual experience had any character of finality. It was rather but the pledge of yet greater gifts to come: even of that knowledge of God which is eternal life (John 17:3). The same thought is expressed, under a more Hebrew image, in the "firstfruits of the Spirit" in Romans 8:23. Grammatically, the "earnest of the Spirit" may be taken as an example of the genitive of apposition, "the earnest which is the Spirit." . . .