The Torah tells us that Hashem remembered Sara as He had promised. The Midrash describes what went on in the Heavenly court. The angels pleaded on behalf of Sara. They pointed out that Lot’s two daughters as well as Hagar, conceived immediately. It was not right that this great lady should suffer any more humiliation, by being childless.
The Gematria of פקד את שרה, that Sara was remembered, according to the Baal Haturim, is equal to אף כל עקרות פקדו, that all barren women were remembered.
We learn from this episode that Hashem always keeps His promises. We must have the patience and faith to accept that things happen according to a Divine plan. But such promises are always fulfilled.
We are living in remarkable times. Rav Shmuel Eliyahu of Tzefat, once spoke of numerous prophecies that were made more than two thousand years ago, that have been fulfilled in our lifetime. This is primarily because of the establishment of the State of Israel. We went through a long and bitter exile, but we knew that the promise of a Jewish homeland would one day be fulfilled.
Like Sara, who waited and was rewarded with a saintly son, we waited and never stopped praying, and we were rewarded with our sacred Holy Land.