In Germany to the Leipsic Disputation - James Aitken Wylie

One day he went, under the influence of these
feelings, to the Church of the Lateran. There is the
Scala Sancta, or Holy Stairs, which tradition says
Christ descended on retiring from the hall of
judgment, where Pilate had passed sentence upon
him. These stairs are of marble, and the work of
conveying them from Jerusalem to Rome was
reported to have been undertaken and executed by
the angels, who have so often rendered similar
services to the Church – Our Lady's House at
Loretto for example. The stairs so transported were
enshrined in the Palace of the Lateran, and every
one who climbs them on his knees merits an
indulgence of fifteen years for each ascent. Luther,
who doubted neither the legend touching the stairs,
nor the merit attached by the bulls of the Popes to
the act of climbing them, went thither one day to
engage in this holy act. He was climbing the steps
in the appointed way, on his knees namely, earning
at every step a year's indulgence, when he was
startled by a sudden voice, which seemed as if it
spoke from heaven, and said, "The just shall live
by faith." Luther started to his feet in amazement.
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