Why did Abraham plant a tamarisk at Beersheba?
Because he had just sworn a covenant of peace at a well in a foreign land, and the tree marked a place of worship — the first place anyone in Scripture calls on God as «the Everlasting God.» The tamarisk only appears three times in the entire Old Testament, and the other two are at the death of Saul.
It is one of the small details in the Abraham cycle that turns out to be enormous when you look at where the word goes.
After Abraham swore the seven-fold oath with Abimelech at the well, and the place was named Beersheba, the chapter closes with this:
וַיִּטַּ֥ע אֶ֖שֶׁל בִּבְאֵ֣ר שָׁ֑בַע וַיִּ֨קְרָא־שָׁ֔ם בְּשֵׁ֥ם יְהוָ֖ה אֵ֥ל עוֹלָֽם
va-yitta eshel bi-Be'er-sheva va-yiqra sham be-shem Yahweh El Olam
"And he planted a tamarisk at Beersheba, and there he called on the name of Yahweh, El Olam." — Genesis 21:33
The word for "tamarisk" is eshel (H815). In the entire Hebrew Old Testament, this word appears in exactly three verses — and none of them are decorative.
The first is here at Genesis 21:33: Abraham plants a tamarisk at Beersheba, calls on the name of Yahweh, and the verse closes with sojourn-language. It is a worship-grove. The Septuagint translators in the third century BC apparently did not recognize the tree-name and rendered it "a cultivated field" — but the Hebrew preserves the tamarisk, and it preserves it for a reason.
The second is 1 Samuel 22:6: "Now Saul was sitting at Gibeah under the eshel, with his spear in his hand, and all his servants standing around him." The next verses describe Saul ordering Doeg the Edomite to slaughter eighty-five priests of Yahweh at Nob. Where Abraham's tamarisk was the place where the divine name was called upon, Saul's tamarisk is the throne where priests of that name are killed.
The third is 1 Samuel 31:13: the men of Jabesh-Gilead recover Saul's burnt bones from the wall of Beth-Shan, carry them home, and bury them under the eshel. The same tree. The same word. Israel's first failed king is buried under it.
Three tamarisks in all of Scripture: Abraham's life-tree, Saul's death-throne, and Saul's grave. The Hebrew text turns one small detail into a three-verse map of the Old Testament's central reversal — from a patriarch calling on the name of God to a king persecuting those who bore that name.
What Abraham did under his tamarisk is the verse's other "first." He called on the name of Yahweh with a two-word divine title: El Olam — the Everlasting God.
El (H410) is the simplest name for God in the Hebrew Bible. Olam (H5769) means duration without end — perpetuity, ancient time, forever. The combination "El Olam" appears in only five Old Testament verses, six total occurrences. Genesis 21:33 is the first. Moses uses it in Psalm 90:2 — "from everlasting to everlasting you are God." Psalm 136 sings it as the great Hallel refrain. Isaiah 40:28 calls on it for the exiles: "the Everlasting God, Yahweh, the Creator of the ends of the earth, does not faint and is not weary." David's last words in 2 Samuel 23:5 name the everlasting covenant. The whole canonical conversation about God-from-eternity begins here, at a well, under a tree, in a foreign land.
The Septuagint renders El Olam with theos aiōnios — the same aiōnios the New Testament uses for eternal life. The Greek word for "age, eternity" that runs through John's Gospel and Paul's letters has its first Old Testament home in Abraham's mouth at Beersheba.
So why the tamarisk? Because it marked the worship. Abraham had no temple, no city, no inheritance in the land yet. What he had was a well he had dug, a treaty he had sworn, and a tree he planted to remember the place. And under that tree he named God as the one outside all time — El Olam — even though he himself, the verse closes, "sojourned in the land of the Philistines many days."
The full study traces the three tamarisks of the Old Testament, the five occurrences of El Olam, and how the everlasting-God epithet finds its way into the Greek New Testament.
How does Mary's Magnificat connect to Sarah at Genesis 21?
Through one Hebrew verb that the Greek Old Testament translates with a single Greek verb — and Luke's birth narrative reuses it in the exact aorist tense the Septuagint used at Sarah's womb. The connection is not thematic resemblance; it is one word traced across the entire canon.
What does «in Isaac shall your seed be called» mean?
It means the promise God gave Abraham would run forward through one specific son — Isaac — and the descendants reckoned to that line would be the heirs of the covenant, not all of Abraham's biological children. Two New Testament writers quote this exact five-word Greek clause to settle who counts as Abraham's true children.
Why did God let Sarah send Hagar and Ishmael away?
Because the inheritance promised to Abraham would pass through one son, not two — and the Hebrew text says that quietly through a pun and an imperative. Sarah used the same verb that drove Adam from Eden and Cain from the ground, and Yahweh told Abraham to listen to her voice.