John symbolises the whole of the Church (i.e. the true Israel of God) with the number 144,000 – 12 times 12,000. Israel is referred to as the thousands of Israel! (Numbers 10:36 Moses said, “Return, O LORD, to the countless thousands of Israel”.) The reference to a seal on their foreheads is reference to their baptism. All of God’s people will be saved. He will not miss out one of His own!