Genesis 21:1

'וה' פקד את שרה וגו AND THE LORD VISITED SARAH —It (Scripture) places this section after the preceding one to teach you that whoever prays for mercy on behalf of another when he himself also is in need of that very thing for which he prays on the other’s behalf, will himself first receive a favorable response from God, for it is said (at end of last chapter), “And Abraham prayed for Abimelech and his wife and they brought forth” and immediately afterwards it states here, “And the Lord remembered Sarah” — i. e. he had already remembered her before he healed Abimelech (Bava Kamma 92a). פקד את שרה כאשר אמר HE REMEMBERED SARAH AS HE SAID — He remembered her by granting her pregnancy. כאשר דבר [HE DID TO SARAH] AS HE HAD SPOKEN — by granting her the birth of a son (Pesikta). Where are the expressions “saying ״ and “speaking” used respectively in regard to these? “Saying” is mentioned in the verse (17:19) “And God said (ויאמר): “nay, but Sarah, thy wife” etc.; — “Speaking“ is mentioned in (15:1) “And the word (דבר “speaking”) of the Lord came to Abraham”, and this was when He made the Covenant between the Pieces where it was stated, “This man (Eliezer) shall not be thine heir, [but one who shall be born from thee shall be thine heir],” and He brought forth this heir from Sarah. ויעש ה' לשרה כאשר דבר AND THE LORD DID UNTO SARAH AS HE HAD SPOKEN — means, spoken to Abraham.

וַֽיהֹוָ֛ה פָּקַ֥ד אֶת־שָׂרָ֖ה כַּאֲשֶׁ֣ר אָמָ֑ר וַיַּ֧עַשׂ יְהֹוָ֛ה לְשָׂרָ֖ה כַּאֲשֶׁ֥ר דִּבֵּֽר׃

And the Lord visited Sara as He had said, and the Lord did to Sara as He had spoken.