God enabled, commissioned (literally anointed), and endorsed Paul's ministry, equipping him for his work.
both us and you: The Holy Spirit identifies all believers as God's own (literally sealed). The Holy Spirit is God's gift to his people (see Romans 8:1–27; Galatians 3:2–7; 5:5–6, 16–26; Ephesians 1:13–14).
a pledge of what is to come: A pledge is a commercial term for a deposit or down payment, guaranteeing full possession (see 2 Corinthians 5:5; Ephesians 1:14).