17:15 And God said to Abraham, "As for Sarai your wife - do not call her name Sarai, for Sarah is her name. (1) I will bless her; indeed, I will give you a son through her; I will bless her and she shall give rise to nations; kings of peoples will rise from her."
Note (1): 17:15 Sarai my princess, implies that she owed her greatness to her status as Abraham's wife. Henceforth, she would be called Sarah, which signifies that she is a "princess to all the nations of the world." She was a princess "par excellence" - to all mankind. (Rashi; Berachos 13a)
21:9 Sarah saw the son of Hagar, the Egyptian, whom she had borne to Abraham, mocking. (2) So she said to Abraham, " Drive out this slavewoman with her son, for the son of that slavewoman shall not inherit with my son, with Isaac!"
Note (2): 21:9 Scripture uses the verb (metsakh - mem, tsadee, khet, koof??)to denote three cardinal sins: idolatry [Exodus 32:6]; adultery [39:7]; and murder[II samuel 2:14]. Thus Ishmael's behavior proved to Sarah that he had become thoroughly corrupt and evil, and he had to be sent away. (Rashi)
Additional note for 21:9-14 Ishmael is expelled. In the ninth of Abraham's Ten Trials, God commanded him to banish Ishmael, because he was a menace to the spiritual health - and perhaps the very life - of Isaac.
21:17 God heard the cry of the youth, (Ishmael)... (3)
Note (3): 21:17 According to the Midrash, the angels pleaded with God not to perform a miracle for Ishmael, because his offspring were destined to persecute and murder Jews, but God responded that he would judge Ishmael only according to his present deeds and not according to what would happen in the future. (Rashi)
Isaiah 27: 1-6
27:1 On that day Hashem will bring punishment with His harsh, great, mighty sword, upon Leviathan, (4) the bar like serpent, and upon Leviathan, the twisting serpent, and He will kill the great fish that is in the sea.
27:2 On that day [people] will sing about [Israel],'A vineyard of fine wine.'
27:3 I am Hashem, Who guards it; I water it frequently; lest [an enemy] attack itnight and day I will guard it.
27:4 I have no wrath;(5) if only I were at war with the weeds and thorns, I would then trample it and set it altogether afire.
27:5 If [Israel] would grasp My stronghold, (6) then he would make peace with Me; peace would he make with Me.
27:6 [Days] are coming when Jacob will take root; Israel will bud and blossom and fill the face of the earth like fruit.
Note (4) 27:1 Leviathan, the giant, earth-girdling serpent-fish symbolizes the great world powers. Isaiah uses the death of the Leviathan to allude to the eventual downfall of all the enemies of Israel. (Radok)
The three descriptions - bar-like, twisting, in the sea - allude to the different natures of the world powers. (Rashi)
Note (5) 27:4 God says that He withholds His total wrath from the nations - the weeds and thorns - because Israel, too, is sinful; if He were to punish the nations as they deserved, justice would dictate that He do the same to Israel. In order to save Israel from fearsome punishment, God relaxes His Attribute of Justice for everyone. (Rashi)
Note (6) 27:5 If only Israel would hold fast to My Torah!
All above verses and commentary are from the Stone Edition of the Tanach.