How do we know that God's wrath is upon those who reject Him?

In 1 Thessalonians 2:16, Paul mentions that those who oppose God's message are 'filling up their sins always' and that 'the wrath is come upon them to the uttermost.' This assertion is established throughout the Bible, from the Old Testament prophecies to the New Testament teachings. God's wrath is revealed against all ungodliness and unrighteousness (Romans 1:18), emphasizing His justice in response to sin. It shows the seriousness of rejecting God and highlights the need for repentance.