Avrohom and Sarah moved to Be'er Sheva and, of course, always kept looking for guests. They would feed their visitors whatever fruits and delicacies they wanted, and even invite them to stay overnight, and they never charged a single cent for the food or lodging.
All Avrohom asked from his guests in return was a simple thank you. But not for himself - for HaShem. He taught everyone to thank HaShem for their food, since He created the fruit trees and the animals, and everything else in the world.
Because they taught others to follow in their ways, Avrohom and Sarah were blessed with a son, just as the three angels had promised. When the baby was born, Sarah was 90 years old and Avrohom was 100! They named their son Yitzchak (meaning "he will laugh"), because his birth brought joy and laughter.
Yitzchak had a brit milah at eight days old, and Sarah nursed him for two years. When he was two, they made a great celebration and invited many guests, including the most important people of their time, to share their happiness and enjoy a grand feast.
It was a strange invitation; on it Avrohom and Sarah asked their guests to bring along their nursing babies. They wanted to prove a point. Some people had been wondering, "Could Yitzchak really be Sarah's son? Isn't she too old to have a baby of her own?"
So Avrohom asked all of the women to bring Sarah their babies, and Sarah nursed them all. Then they saw with their own eyes that HaShem had miraculously made Sarah like a young woman again, and everyone knew that little Yitzchak was indeed her child.
