Acts 1:15
Acts 1:1515In those days Peter stood up among the brothers (a gathering of about a hundred and twenty) and said,
The Watchtower treats ("there was a crowd of persons all together about 120") as straightforward narrative — establishing the size of the pre-Pentecost Jerusalem church. It is not deployed as a distinctive proof-text in its own right and is not typically connected to the / "earth full of the knowledge of Jehovah" prophecies, which the Watchtower defers entirely to a future millennial fulfilment.
is the starting point for a remarkable trajectory. 120 disciples in Jerusalem in AD 33. By (written roughly AD 60), Paul can describe the gospel as "bearing fruit and increasing in all the world." By he can say the gospel has been "preached in all creation under heaven." Today, roughly a third of the world's population identifies as Christian; the Bible has been translated into over 700 languages.
and both use the same imagery: "the earth will be filled with the knowledge of Jehovah as the waters cover the sea" — progressive filling, not sudden event. Waters rise gradually. The Watchtower applies the promise entirely to a future post-Armageddon paradise, which requires reading the prophecy as having zero fulfilment between AD 33 and the end of the age. But the trajectory from — 120 people in an upper room — to today's two billion confessing Christians is exactly the waters-covering-the-sea pattern Isaiah described. The already / not yet framework is not a Protestant novelty; it is how the apostles themselves read the Old Testament promises. The gospel's spread is the ongoing fulfilment of , visible in a way the Watchtower's deferred-only model cannot accommodate.