ויתפלל אברהם אל האלקים וירפא אלקים את אבימלך... וד' פקד את שרה
Rashi notes the juxtaposition of Sarah Imeinu’s conception and giving birth to Yitzchak Avinu upon Avraham Avinu’s prayer on behalf of Avimelech. He explains that the Torah put this passage (Sarah’s conception and giving birth) next to the incident of Avimelech to teach that whoever seeks mercy by praying for his friend, while he himself (the individual praying) needs that same thing (for which he is praying on behalf of his friend), he (the one praying), is answered first. Avimelech was in need – Avraham prayed for him; thus, he was answered by Hashem – before Avimelech. Imagine two people…