_e.g._, fear of
punishment, forgiveness is to be obtained only by the worthy reception
of Penance. In other words, the penitent must confess his sin to a duly
authorized priest, express his contrition, accept the penance enjoined
by the confessor for the satisfaction of sin and be absolved by virtue
of the words of Christ: "Whose sins you shall forgive they are forgiven
and whose sins you shall retain, they are retained."

All this is most beautifully expressed by Dante in his description of
the Gate of St. Peter and its angelic keeper:

"The lowest stair was marble white, so smooth
And polish'd that therein my mirror'd form
Distinct I saw. The next of hue more dark
Than sablest grain, a rough and singed block,
Cracked lengthwise and across. The third, that lay
Massy above, seemed prophyry, that flam'd
Red as the life-blood spouting from a vein.
On this God's angel either foot sustain'd,
Upon the threshold seated, which appear'd
A rock of diamond. Up the trinal steps
My leader cheerly drew me. 'Ask,' said he,
'With humble heart, that he unbar the bolt.'
Piously at his holy feet devolv'd
I cast me, praying him for pity's sake
That he would open to me: but first fell
Thrice on my bosom prostrate. Seven times
The letter, that denotes the inward stain,
He on my forehead with the blunted point
Of the drawn sword inscrib'd. And 'Look,' he cried,
'When enter'd, that thou wash these scars away.'
Ashes, or earth ta'en dry out of the ground,
Were of one colour with the robe he wore.
From underneath that vestment forth he drew
Two keys of metal twain: the one was gold,
Its fellow silver. With the pallid first,
And next the burnish'd, he so ply'd the gate,
As to content me well. 'Whenever one
Faileth of these, that in the keyhole straight
It turn not, to this alley then expect
Access in vain.' Such were the words he spake,
'One is more precious; but the other needs
Skill and sagacity, large share of each,
Ere its good task to disengage the knot
Be worthily perform'd. From Peter these
I hold, of him instructed, that I err
Rather in opening than in keeping fast,
So but the suppliant at my feet implore.'
Then of that hallow'd gate he thrust the door,
Exclaiming, 'Enter, but this warning hear:
He forth again departs who looks behind.'"
(IX, 75.)

The allegory back of these words is put forth in clear language by Maria
F. Rossetti.