As soon as Joab had left David,

2 Samuel 20:8-10
And while they were at the great stone in Gibeon, Amasa joined them. Now Joab was dressed in military attire, with a dagger strapped to his belt. And as he stepped forward, he slipped the dagger from its sheath. / “Are you well, my brother?” Joab asked Amasa. And with his right hand Joab grabbed Amasa by the beard to kiss him. / Amasa was not on guard against the dagger in Joab’s hand, and Joab stabbed him in the stomach and spilled out his intestines on the ground. And Joab did not need to strike him again, for Amasa was dead. Then Joab and his brother Abishai pursued Sheba son of Bichri.

1 Kings 2:5-6
Moreover, you know what Joab son of Zeruiah did to me—what he did to Abner son of Ner and Amasa son of Jether, the two commanders of the armies of Israel. He killed them in peacetime to avenge the blood of war. He stained with the blood of war the belt around his waist and the sandals on his feet. / So act according to your wisdom, and do not let his gray head go down to Sheol in peace.

Psalm 41:9
Even my close friend whom I trusted, the one who shared my bread, has lifted up his heel against me.

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he sent messengers after Abner,

1 Samuel 19:11-17
Then Saul sent messengers to David’s house to watch him and kill him in the morning. But David’s wife Michal warned him, “If you do not run for your life tonight, tomorrow you will be dead!” / So Michal lowered David from the window, and he ran away and escaped. / Then Michal took a household idol and laid it in the bed, placed some goat hair on its head, and covered it with a garment. …

Judges 16:18-21
When Delilah realized that he had revealed to her all that was in his heart, she sent this message to the lords of the Philistines: “Come up once more, for he has revealed to me all that is in his heart.” Then the lords of the Philistines came to her, bringing the money in their hands. / And having lulled him to sleep on her lap, she called a man to shave off the seven braids of his head. In this way she began to subdue him, and his strength left him. / Then she called out, “Samson, the Philistines are here!” When Samson awoke from his sleep, he thought, “I will escape as I did before and shake myself free.” But he did not know that the LORD had departed from him. …

Proverbs 1:10-15
My son, if sinners entice you, do not yield to them. / If they say, “Come along, let us lie in wait for blood, let us ambush the innocent without cause, / let us swallow them alive like Sheol, and whole like those descending into the Pit. …

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who brought him back from the well of Sirah.

2 Samuel 17:18-21
But a young man did see them and told Absalom. So the two left quickly and came to the house of a man in Bahurim. He had a well in his courtyard, and they climbed down into it. / Then the man’s wife took a covering, spread it over the mouth of the well, and scattered grain over it so nobody would know a thing. / When Absalom’s servants came to the woman at the house, they asked, “Where are Ahimaaz and Jonathan?” “They have crossed over the brook,” she replied. The men searched but did not find them, so they returned to Jerusalem. …

2 Samuel 23:15-17
David longed for water and said, “Oh, that someone would get me a drink of water from the well near the gate of Bethlehem!” / So the three mighty men broke through the Philistine camp, drew water from the well near the gate of Bethlehem, and brought it back to David. But he refused to drink it; instead, he poured it out to the LORD, / saying, “Far be it from me, O LORD, to do this! Is this not the blood of the men who risked their lives?” So he refused to drink it. Such were the exploits of the three mighty men.

Genesis 24:11-20
As evening approached, he made the camels kneel down near the well outside the town at the time when the women went out to draw water. / “O LORD, God of my master Abraham,” he prayed, “please grant me success today, and show kindness to my master Abraham. / Here I am, standing beside the spring, and the daughters of the townspeople are coming out to draw water. …

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But David was unaware of it.

1 Kings 2:32-33
The LORD will bring his bloodshed back upon his own head, for without the knowledge of my father David he struck down two men more righteous and better than he when he put to the sword Abner son of Ner, commander of Israel’s army, and Amasa son of Jether, commander of Judah’s army. / Their blood will come back upon the heads of Joab and his descendants forever; but for David, his descendants, his house, and his throne, there shall be peace from the LORD forever.”

Psalm 64:2-6
Hide me from the scheming of the wicked, from the mob of workers of iniquity, / who sharpen their tongues like swords and aim their bitter words like arrows, / ambushing the innocent in seclusion, shooting suddenly, without fear. …

Proverbs 26:24-26
A hateful man disguises himself with his speech, but he lays up deceit in his heart. / When he speaks graciously, do not believe him, for seven abominations fill his heart. / Though his hatred is concealed by deception, his wickedness will be exposed in the assembly.

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2 Samuel 20:9-10
“Are you well, my brother?” Joab asked Amasa. And with his right hand Joab grabbed Amasa by the beard to kiss him. / Amasa was not on guard against the dagger in Joab’s hand, and Joab stabbed him in the stomach and spilled out his intestines on the ground. And Joab did not need to strike him again, for Amasa was dead. Then Joab and his brother Abishai pursued Sheba son of Bichri.

2 Samuel 2:18-23
The three sons of Zeruiah were there: Joab, Abishai, and Asahel. Now Asahel was fleet of foot like a wild gazelle, / and he chased Abner, not turning to the right or to the left in his pursuit. / And Abner glanced back and said, “Is that you, Asahel?” “It is,” Asahel replied. …

2 Samuel 3:27-30
When Abner returned to Hebron, Joab pulled him aside into the gateway, as if to speak to him privately, and there Joab stabbed him in the stomach. So Abner died on account of the blood of Joab’s brother Asahel. / Afterward, David heard about this and said, “I and my kingdom are forever guiltless before the LORD concerning the blood of Abner son of Ner. / May it whirl over the head of Joab and over the entire house of his father, and may the house of Joab never be without one having a discharge or skin disease, or one who leans on a staff or falls by the sword or lacks food.” …

1 Chronicles 11:6
Now David had said, “Whoever is the first to strike down a Jebusite will become chief commander.” And Joab son of Zeruiah went up first, and he became the chief.