The Just and the Justifier

It was to show his righteousness at the present time, so that he might be just and the justifier of the one who has faith in Jesus. (Romans 3:26 ESV)

But now the righteousness of God has been clearly revealed [independently and completely] apart from the Law, though it is [actually] confirmed by the Law and the [words and writings of the] Prophets. This righteousness of God comes through faith in Jesus Christ for all those [Jew or Gentile] who believe [and trust in Him and acknowledge Him as God's Son]. There is no distinction, since all have sinned and continually fall short of the glory of God, and are being justified [declared free of the guilt of sin, made acceptable to God, and granted eternal life] as a gift by His [precious, undeserved] grace, through the redemption [the payment for our sin] which is [provided] in Christ Jesus, whom God displayed publicly [before the eyes of the world] as a [life-giving] sacrifice of atonement and reconciliation (propitiation) by His blood [to be received] through faith. This was to demonstrate His righteousness [which demands punishment for sin], because in His forbearance [His deliberate restraint] He passed over the sins previously committed [before Jesus' crucifixion]. It was to demonstrate His righteousness at the present time, so that He would be just and the One who justifies those who have faith in Jesus [and rely confidently on Him as Savior]. (Romans 3:21-26 Amplified Bible)

God can be the just (He punishes all sin) and the justifier (He forgives all sin) because He had sent His only begotten Son to die for our sins on the cross.

For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. (John 3:16 KJV)

For Christ also suffered once for sins, the righteous for the unrighteous, to bring you to God. He was put to death in the body but made alive in the Spirit. (1 Peter 3:18 NIV)