All the nations, people groups, tribes and families, tongues and language groups of the earth are to be converted from enemies and strangers into friends and family. They will all praise the Lord when they see the mercy and truth of the One True God.
“Grace and Truth came by Jesus Christ.” So says John. Mercy and truth is a simple translation of “steadfast love and faithfulness.” Mercy and truth are mentioned together and praised together many times. “Mercy and truth kissed each other.” Mercy and truth are even seen as agents of God, or messengers, sent by Him to meet a person who prays for help.
“Mercy” is the essential character of God which moves Him to decide to send His Son, the Savior, into the world. “Truth” is the faithful, promise-keeping character of God that actually carries out that desire and will of God in real time and Christmas happens.
When the peoples of the world hear the Gospel and see Jesus they see that the merciful kindness of God is great and His faithfulness lasts forever; then they praise the Lord, like us, who have already seen mercy and truth in Jesus.