From Charlotte's Web
[Six weeks later
] Wilbur was what the farmers call a "spring pig", which means he was born in springtime. By the time he was six weeks old, he'd grown so, you'd never have known he started life as a runt. Wilbur had gotten so big, in fact, that John Arable decided that it was time he stopped being a pet, and start being a pig.
[At the Arable house
] He's got to go, Fern.
You've had your fun raising a baby pig, but Wilbur's got to be sold. He's not a baby anymore and his brothers and sisters are already sold.