What does it mean that the apostles witnessed Jesus on a cloud covered mountain clothed in dazzling light in dialogue with Moses and Elijah?
On the mountain in the cloud and darkness, we are reminded of the transcendent truth revealed in Christ, that this is hidden wisdom given only in faith, and that faith itself is like the ascending a mountain - each step raises us higher into God's mystery and deeper into purity of heart. In the light and glory of this moment, we see the Gospel of Christ contemplated in the Law and the Prophets. As Christians, we must not be ignorant of the Bible but prayerfully reflect with the eye of faith on the wisdom of God which imbues the Sacred Page.
What does it mean that the apostles heard the command of the Father?
It means the ear of the heart must be open to the Word of Truth in all the hidden disguises He comes to us. When we find the Beloved Son in those God has entrusted to us, we must never leave Him, we must strive to serve to Him with all our strength, and no matter the cost we must follow Him in everything. He alone is our hope on prayer's pilgrimage from Mt. Tabor to the Hill of Calvary.