"From fairest creatures we desire increase / That thereby beauty's rose might never die,"
We want the best-looking people to have children so that their beauty can be appreciated by future generations,
"But as the riper should by time decease / His tender heir might bear his memory:"
For once the elder has passed away, his young will share the memory of his ancestor's beauty (and may look like the elder):
"But thou, contracted to thine own bright eyes / Feed'st thy light's flame with self-substantial fuel,"
But you, obsessed with your own beauty, selfishly consume all of that beauty's light,
"Making a famine where abundance lies / Thy self thy foe, to thy sweet self too cruel:"
Depriving the world of that beauty when there is plenty to be had by all; you are your own enemy, you are cruel to your own sweet self, for not having a child to carry on your memory.
"Thou that art now the world's fresh ornament / And only herald to the gaudy spring,"
You who are now a beautiful thing on earth, and the one who announces the coming of spring,
"Within thine own bud buriest thy content / And, tender churl, mak'st waste in niggarding:"
Are burying your self-satisfied beauty within yourself, and wasting it by being selfish.
"Pity the world, or else this glutton be / To eat the world's due, by the grave and thee."
Have pity on the world and bear a child; otherwise you are a glutton, keeping your beauty to yourself by taking it with you to the grave.
Why is he saying it?
Sonnets 1-126 comprise the first unit of Shakespeare's sonnets, although the second unit is considerably smaller, comprising only 28 sonnets. We often call sonnets 1-126 the "fair lord sonnets" because...