Isaiah 6:8 captures the purest picture of calling: God speaks into an open room, and the question is simply who will go. Isaiah had just been undone by the holiness of God and declared himself ruined. Immediately after being cleansed, he hears the invitation and responds. Calling in Scripture never waits for you to feel ready. It asks while you are still overwhelmed.
Matthew 28:19–20 — the Great Commission — is built on a grammatical foundation most English readers miss. The main verb is not "go." It is "make disciples." Going, baptizing, and teaching are participles modifying that central command. The call is not primarily to movement — it is to formation. You are sent in order to form others into what Christ has formed you into.
Jeremiah 1:5 makes explicit what is implied throughout Scripture: calling precedes existence. "Before I formed thee in the belly I knew thee." Knowing, sanctifying, and ordaining all happen before birth. Romans 11:29 adds that "the gifts and calling of God are without repentance" — the Greek ametamelētos means irrevocable, never taken back. God does not call and then reconsider. The appointment stands.
Commentary is from a charismatic Protestant perspective, drawing on KJV text and public-domain sources including Spurgeon, Andrew Murray, and Matthew Henry.