Below are three biblical arguments against universalism (and an extra one for further reading!). While they offer more than simple proof texts, it would take a much longer article to develop them more fully. Even so, I trust that you will find them useful and persuasive. Let’s first look at some relevant context, and then dive into the arguments themselves.
Personal eschatology—the study of the final fate of human beings—should be embedded within cosmic eschatology, the study of the final state of God’s created order. God is redeeming the cosmos, and human beings within it (see Rom 8:18-25). Universalists and conditionalists both agree that God will redeem the cosmos as a whole. But universalists also claim that God will eventually redeem every human being that will have ever lived, while our claim as conditionalists is that God’s work of “new creation” purposefully excludes some human beings. Despite knowing enough about the immortal God and realizing that they ultimately deserve death they still reject him (Rom 1:18-23; 32). They disobey the gospel (1 Pet 4:17; 2 Thess 1:8; Rom 10:16), and so fail to respond obediently in repentance and faith to the knowledge of God and his offer of salvation (Acts 6:7; Rom 1:5; 16:26). They love sin rather than goodness, themselves rather than God, and are “disqualified regarding the faith” (John 3:20; 2 Tim 3:2-8).