St Leo's application for us is that Christians must have both faith and works. That is, we must believe and obey. This is yet another example that demonstrates the early Church taught "faith and works" and not the Protestant formulation of "faith alone."
Here's Saint Leo:
This came to be fulfilled, as we know, from the time when the star beckoned the three wise men out of their distant country and led them to recognise and adore the King of heaven and earth. The obedience of the star calls us to imitate its humble service: to be servants, as best we can, of the grace that invites all men to find Christ.For more about the Catholic doctrine of justification by faith and works in accord with the teachings of Saint Paul, please see my new book: The Catholic Perspective on Paul.
Dear friends, you must have the same zeal to be of help to one another; then, in the kingdom of God, to which faith and good works are the way, you will shine as children of the light: through our Lord Jesus Christ, who lives and reigns with God the Father and the Holy Spirit for ever and ever. Amen.
Pope Saint Leo the Great, Sermon 3 in Epiphania Domini, 1-3. 5: PL 54, 240-244.