30 “There have been seen Your steps, O God”. The steps are those wherewith You have come through the world, as though in that chariot You were going to traverse the round world; which chariot of clouds He intimates to be His holy and faithful ones in the Gospel, where He says, “From this time you shall see the Son of Man coming in the clouds.” Leaving out that coming wherein He shall be Judge of quick and dead, “From this time,” He says, “you shall see the Son of Man coming in clouds.” These “Your steps have been seen,” that is, have been manifested, by the revealing the grace of the New Testament. Whence has been said, “How beautiful are the feet of them that proclaim peace, that proclaim good things!” For this grace and those steps were lying hid in the Old Testament: but when there came the fullness of time, and it pleased God to reveal His Son, that He might be proclaimed among the Gentiles, “there were seen Your steps, O God: the steps of my God, of the King who is in the holy place.” In what holy place, save in His Temple? “For the Temple of God is holy,” he says, “which you are.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)