When forty winters shall besiege thy brow,
And dig deep trenches in thy beauty’s field,
Thy youth’s proud livery, so gazed on now,
Will be a tatter’d weed, of small worth held:
Then being ask’d where all thy beauty lies,
Where all the treasure of thy lusty days,
To say, within thine own deep-sunken eyes,
Were an all-eating shame and thriftless praise.
How much more praise deserved thy beauty’s use,
If thou couldst answer ‘This fair child of mine
Shall sum my count and make my old excuse,’
Proving his beauty by succession thine!
This were to be new made when thou art old,
And see thy blood warm when thou feel’st it cold.
The poet looks ahead to the time when the youth will have aged, and uses this as an argument to urge him to waste no time, and to have a child who will replicate his father and preserve his beauty. The imagery of ageing used is that of siege warfare, forty winters being the besieging army, which digs trenches in the fields before the threatened city. The trenches correspond to the furrows and lines which will mark the young man’s forehead as he ages. He is urged not to throw away all his beauty by devoting himself to self-pleasure, but to have children, thus satisfying the world, and Nature, which will keep an account of what he does with his life.