Without an appearance of angels, and strengthened by the Word alone, the martyrs met death for the sake of the name of Christ. Why should we, too, not be satisfied with the same thing? Baptism is a sufficiently manifest and clear appearance. So are the Eucharist, the Keys, the ministry of the Word. They are equal to — yes, they even surpass — all the appearances of all angels, in comparison with which Abraham had only droplets and crumbs.
LW, AE vol. 4, p. 126