When you turn the page from the end of the Old Testament to the beginning of the New Testament, it can seem like you are entering a different world. And in some respects that is true; four hundred years have passed, the Jews are ruled over by the Romans rather than the Persians, and there are new groups of people such as Pharisees and Sadducees. To these some would add at least one more difference—that the God of the Old Testament is different from the God of the New Testament.
One common way this belief is stated is to claim that the God of the Old Testament is a god of wrath, whereas the God of the New Testament is a god of love. While on the surface this claim may seem plausible, a closer look at the Bible shows it is seriously mistaken. The God who pours out his wrath against sin in the Old Testament is the same God who will inflict the vengeance of eternal punishment on those who do not believe in his Son Jesus (2 Thes 1:5–10). At the same time, the God who in the New Testament is described as loving the world enough to send his Son for their salvation (John 3:16) is the same God who revealed himself to Moses as “merciful and gracious, slow to anger, and abounding in steadfast love and faithfulness, keeping steadfast love for thousands, forgiving iniquity and transgression and sin” (Exod 34:6–7). From Genesis to Revelation we see both God's stunning love and his terrifying wrath against sin and wickedness.
In fact, the New Testament authors consistently claim that the God revealed in the Old Testament in the same God who is now revealing himself in and through Jesus Christ. Referring to Jesus as the Word, John writes, “In the beginning was the Word, and the Word was with God, and the Word was God. He was in the beginning with God. All things were made through him, and without him was not any thing made that was made” (John 1:1–3). Later in that same chapter John writes, “No one has ever seen God; the only God, who is at the Father's side, he [i.e., the Word] has made him known” (John 1:18). John's point is clear: the God of the Old Testament has taken on flesh and lived among us in the person of Jesus Christ.
As the earliest followers of Jesus began preaching the good news of his death and resurrection, they repeatedly emphasized that the God of the Old Testament had fulfilled his promises in and through Jesus Christ. Peter asserts that Jesus was “delivered up according to the definite plan and foreknowledge of God” (Acts 2:23) and that “The God of Abraham, the God of Isaac, and the God of Jacob, the God of our fathers, glorified his servant Jesus” (Acts 3:13). Paul argues that all who believe in Jesus Christ, regardless of their ethnicity or gender, inherit the blessings that God promised to Abraham (Gal 3:1–5:1). He can even go so far as to say that “all the promises of God find their Yes” in Jesus Christ (2 Cor 1:20).
So, rather than seeing the God of the Old Testament as full of wrath and the God of the New Testament as full of love, the truth is that God has not changed (Mal 3:6; James 1:17). Psalm 102:25–27 notes that in contrast to this world, which will pass away, “you are the same, and your years have no end.” Hebrews 1:10–12 applies that very same language to Jesus Christ, who later in that same letter is described as “the same yesterday and today and forever” (Heb 13:8). God's character as revealed in the Old Testament comes into even clearer focus and expression in the New Testament, because he has taken on flesh in the person of Jesus Christ.