Mark 9: 1-5
1 And after six days Jesus taketh with him Peter and James and John, and leadeth them up into an high mountain apart by themselves, and was transfigured before them. 2 And his garments became shining and exceeding white as snow, so as no fuller upon earth can make white. 3 And there appeared to them Elias with Moses; and they were talking with Jesus. 4 And Peter answering, said to Jesus: Rabbi, it is good for us to be here: and let us make three tabernacles, one for thee, and one for Moses, and one for Elias. 5 For he knew not what he said: for they were struck with fear.
This one strikes me as though Christ is mingling in a way between the two covenants. One is already in place and the other is still working its way to completion on earth. With Moses and Elijah God had a covenant and laws, a certain structure in place so that the faithful wouldn't be wandering around wondering which way was up.
Peter, as Christ's Vicar who will be left on earth to head the church represents the new law and authority of Christ. James to me represents Christ's great work and the works of his followers. And John, to whom was given Mary to care for, represents Christ's commandment to love one another as he loved us. So when I think of this mystery three thoughts eventually come to mind: Love, Work, and Obedience.