Why does the Bible show two different versions of God if he is One unchanging God?

It is very common to feel a sense of contrast between the sweeping judgments of the Old TestamentThe Old Testament is the first major division of the Christian Bible, containing the sacred writings of Israel — creation, covenant, law, prophecy, wisdom, and the entire pre‑Messianic history that prepares the way for Christ. More and the gentle compassion of JesusJesus of Nazareth, also called the Christ or the Messiah, is the central figure of the New Testament and the fulfillment of God’s redemptive plan. Born in the line of David, He taught with divine authority, performed miracles, and revealed the kingdom of God. More in the Gospels, leading many to wonder if Scripture depicts two distinct deities. However, when we read both Testaments holistically, we discover that God’s character remains completely unified, unchanging, and consistent from beginning to end. The Old TestamentThe Old Testament is the first major division of the Christian Bible, containing the sacred writings of Israel — creation, covenant, law, prophecy, wisdom, and the entire pre‑Messianic history that prepares the way for Christ. More is saturated with breathtaking descriptions of God’s tender mercy, patience, and steadfast love, revealing Him as a Father who is slow to anger and abounding in lovingkindness, repeatedly holding back judgment to plead with wayward people. Conversely, the New TestamentThe New Testament is the collection of twenty‑seven inspired books revealing the fulfillment of God’s redemptive plan through Jesus Christ, the birth of the church, and the arrival of the new covenant promised in the Old Testament. More does not discard God’s holy wrath or justice; JesusJesus of Nazareth, also called the Christ or the Messiah, is the central figure of the New Testament and the fulfillment of God’s redemptive plan. Born in the line of David, He taught with divine authority, performed miracles, and revealed the kingdom of God. More Himself spoke more frequently about hell, judgment, and the consequences of unrepentant sin than any prophet before Him, and the book of Revelation portrays ChristJesus of Nazareth, also called the Christ or the Messiah, is the central figure of the New Testament and the fulfillment of God’s redemptive plan. Born in the line of David, He taught with divine authority, performed miracles, and revealed the kingdom of God. More executing final, righteous judgment against all evil. The difference between the testaments is not a change in God’s nature, but a progression in His covenantal plan of redemption. God has always been simultaneously holy in His justice and boundless in His love. The Lord declares in MalachiMalachi is the final prophet of the Old Testament, speaking to a post‑exilic Israel struggling with spiritual apathy. His message confronts corrupt worship, unfaithful leadership, and fading devotion, while pointing forward to the coming messenger who will prepare the way of the Lord. More that He does not change, and Hebrews affirms that Jesus ChristJesus of Nazareth, also called the Christ or the Messiah, is the central figure of the New Testament and the fulfillment of God’s redemptive plan. Born in the line of David, He taught with divine authority, performed miracles, and revealed the kingdom of God. More is the same yesterday, today, and forever. Rather than revealing two conflicting versions of God, the entire Bible reveals the singular, unchanging Lord whose perfect justice and infinite mercy meet harmoniously at the cross of ChristJesus of Nazareth, also called the Christ or the Messiah, is the central figure of the New Testament and the fulfillment of God’s redemptive plan. Born in the line of David, He taught with divine authority, performed miracles, and revealed the kingdom of God. More, where God’s wrath against sin was fully satisfied so His forgiving love could be lavishly poured out.