41. And Adonijahu heard (and all those who were summoned with him and they had finished eating). And Joab head the sound of the horn and said, “why is the city’s voice grumbling?”
42. While he was still speaking, dude! Jonathan ben Abiathar (the priest) came and Adonijahu said, “come, for a mighty man are you and good tidings you will bear!”
43. And Jonathan answered Adonijahu, “truly, our lord King David has made Solomon king.
44. “And the king sent with him Zadok the priest and Nathan the prophet and Benaiahu ben Jehoiada and the Cherethites and the Pelethites and they had him ride upon the king’s mule.
45. “And they anointed him, Zadok the priest and Nathan the prophet, to (be) king at Gihon and they went up from there happily and agitated the city. This is the sound that you heard.
46. “And also Solomon sat on the throne of the kingdom.
47. “And also the servants of the king came to bless our lord King David, saying ‘may your God make the name of your son Solomon greater than your name and increase his throne more than your throne.’ And the king prostrated on his bed.
48. “And thus spoke the king, ‘blessed is Yhwh, Israel’s God, who gave today the one sitting on my throne and my eyes are seeing (it).'”
49. And they trembled and got up, all those who had been called to Adonijahu, and they went, each to his path.
50. And Adonijahu was afraid from before Solomon and he got up and went and grasped the horns of the altar.
51. And it was told to Solomon, saying, “dude! Adonijahu fears King Solomon and, dude! He has grasped the horns of the altar, saying, ‘King Solomon should swear to me just as today that he will not kill his servant with the sword.'”
52. And Solomon said, “if he will be to me a son of honor, nothing will fall from his hair to the ground. But if wickedness is found in him, he will die.”
53. And King Solomon sent and let him be brought down from on the altar and he came and did obeisance to King Solomon. And Solomon said to him, “go to your house!”

Comments on the Text
Verse 48 opens again with a singular verb and a plural subject, making the syntax somewhat awkward, particularly with the reference to their finishing eating. Why is that relevant? First Adonijahu hears, though it is not clear what. Then Joab hears, and here it is clear: he hears the sounds of horns and, based on his inquiry, the uproar in the city.
In response to this, suddenly and conveniently (from a narrative perspective) the son of the priest allied with Adonijahu arrives from off of the scene. Adonijahu presumes that he will provide an auspicious report of what is going on and inquires what is up.
His response is prompt and initially to the point: King David has made Solomon king. The description of King David as “our lord” can be understood in a variety of ways. Does this mean that Adonijahu never supposed himself a usurper? Is this comment to undercut his position? Is this reference to protect him from people who would want to accuse him of usurpation? No evidence is provided, but it is interesting that here King David is “our lord” to the people assembled around Adonijahu.
Verses 44-45 more or less describe the scene from 38-40. The real change comes in verse 46, which opens a whole passage of material that the reader has thus far heard nothing about other than in Nathan’s plan. This is the first time the reader hears of Solomon sitting on the king’s throne. The ductus of this new material continues in verses 47-48, which include new blessings and speeches from the people involved in Solomon’s accession. Suddenly the king is there and expresses his thanks that he lived to experience this event. After citing the king’s speech, Jonathan concludes his recitation of recent events.
The reaction to this speech is fear and abandonment in vv. 49-50. First Adonijahu is abandoned and then he flees to the altar. This altar probably refers to the one in 2 Sam 24, as no other altar has been mentioned thus far. Presumably Adonijahu thinks he will be safe in front of the altar. While it works in this case, this view is somewhat shortsighted, as will become clear in the next chapter.
The episode concludes with Solomon, now officially called the king (though not exclusively), reacting to Adonijahu in vv. 51-53. Solomon promises only to kill him if wickedness is found in him. The reader knows what this means and this expectation is fulfilled in the next chapter. With this, power has now officially transferred from David to Solomon. It should have been David as king who reacted to Adonijahu, but this task is left to Solomon. David never says anything about it in the biblical story before his death. He never mentions this episode with Adonijahu. David only does two more things in this recounting of his reign before Solomon ultimately takes over: 1) he admonishes Solomon and 2) dies.