And Sadoc the son of Achitob, and Achimelech the son of Abiathar, were the priests: and Saraias was the scribe:

And Zadok and Abiathar, the son of Ahimelech, the son of Ahitub, were priests; and Seraiah was the scribe;

Seraiah - the scribe - Most likely the king's private secretary. See 1-Chronicles 24:3 (note).

And Zadok the son of Ahitub, and Ahimelech the son of Abiathar, were the priests,.... Not high priests, as Josephus (i) suggests, for there was only one high priest at a time; indeed there was a "sagan", or deputy priest, on occasion; and so Abarbinel says that Zadok was the high priest, and Ahimelech his second or deputy; but the truth of the case was this, Abiathar was high priest only, and continued so until the time of Solomon, when he was thrust out of his office, and Zadok put into it; and Ahimelech his son and Zadok were the principal priests under him, the one of the family of Ithamar, the other of Eleazar; so the Targum on 1-Chronicles 18:16 calls them "sagans", or deputies of the high priesthood. Zadok is mentioned first, though Ahimelech was the son of the present high priest, because he was in great favour with David, as afterwards with Solomon, in whose days the high priesthood was translated to him; the family of Eli being now upon the decline, and near being removed from the high priesthood, as was foretold by Samuel it should:
and Seraiah was the scribe; or secretary of state; in 1-Chronicles 18:16 he is called Shavsha; he seems to have had two names.
(i) Ut supra, (Antiqu. l. 7. c. 5.) sect. 4.

Zadok . . . and Ahimelech . . . were the priests--On the massacre of the priests at Nob, [1-Samuel 22:19], Saul conferred the priesthood on Zadok, of the family of Eleazar (1-Chronicles 6:50), while David acknowledged Ahimelech, of Ithamar's family, who fled to him. The two high priests exercised their office under the respective princes to whom they were attached. But, on David's obtaining the kingdom over all Israel, they both retained their dignity; Ahimelech officiating at Jerusalem, and Zadok at Gibeon (1-Chronicles 16:39).

Zadok the son of Ahitub, of the line of Eleazar (1-Chronicles 6:8; 1-Chronicles 6:11-12), and Ahimelech the son of Abiathar, were cohanim, i.e., officiating high priests; the former at the tabernacle at Gibeon (1-Chronicles 16:39), the latter probably at the ark of the covenant upon Mount Zion. Instead of Ahimelech, the Chronicles have Abimelech, evidently through a copyist's error, as the name is written Ahimelech in 1-Chronicles 24:3, 1-Chronicles 24:6. But the expression "Ahimelech the son of Abiathar" is apparently a very strange one, as Abiathar was a son of Ahimelech according to 1-Samuel 22:20, and in other passages Zadok and Abiathar are mentioned as the two high priests in the time of David (2-Samuel 15:24, 2-Samuel 15:35; 2-Samuel 17:15; 2-Samuel 19:12; 2-Samuel 20:25). This difference cannot be set aside, as Movers, Thenius, Ewald, and other suppose, by transposing the names, so as to read Abiathar the son of Ahimelech; for such a solution is precluded by the fact that, in 1-Chronicles 24:3, 1-Chronicles 24:6, 1-Chronicles 24:31, Ahimelech is mentioned along with Zadok as head of the priests of the line of Ithamar, and according to 1-Chronicles 24:6 he was the son of Abiathar. It would therefore be necessary to change the name Ahimelech into Abiathar in this instance also, both in 1-Chronicles 24:3 and 1-Chronicles 24:6, and in the latter to transpose the two names. But there is not the slightest probability in the supposition that the names have been changed in so many passaGes. We are therefore disposed to adopt the view held by Bertheau and Oehler, viz., that Abiathar the high priest, the son of Ahimelech, had also a son named Ahimelech, as it is by no means a rare occurrence for grandfather and grandson to have the same names (vid., 1-Chronicles 6:4-15), and also that this (the younger) Ahimelech performed the duties of high priest in connection with his father, who was still living at the commencement of Solomon's reign (1-Kings 2:27), and is mentioned in this capacity, along with Zadok, both here and in the book of Chronicles, possibly because Abiathar was ill, or for some other reason that we cannot discover. As Abiathar was thirty or thirty-five years old at the time when his father was put to death by Saul, according to what has already been observed at 1-Samuel 14:3, and forty years old at the death of Saul, he was at least forty-eight years old at the time when David removed his residence to Mount Zion, and might have had a son of twenty-five years of age, namely the Ahimelech mentioned here, who could have taken his father's place in the performance of the functions of high priest when he was prevented by illness or other causes. The appearance of a son of Abiathar named Jonathan in 2-Samuel 15:27; 2-Samuel 17:17, 2-Samuel 17:20, is no valid argument against this solution of the apparent discrepancy; for, according to these passages, he was still very young, and may therefore have been a younger brother of Ahimelech. The omission of any allusion to Ahimelech in connection with Abiathar's conspiracy with Adonijah against Solomon (1-Kings 1:42-43), and the reference to his son Jonathan alone, might be explained on the supposition that Ahimelech had already died. But as there is no reference to Jonathan at the time when his father was deposed, no stress is to be laid upon the omission of any reference to Ahimelech. Moreover, when Abiathar was deposed after Solomon had ascended the throne, he must have been about eighty years of age. Seraiah was a scribe. Instead of Seraiah, we have Shavsha in the corresponding text of the Chronicles, and Sheva in the parallel passage 2-Samuel 20:25. Whether the last name is merely a mistake for Shavsha, occasioned by the dropping of שׁ, or an abbreviated form of Shisha and Shavsha, cannot be decided. Shavsha is not a copyist's error, for in 1-Kings 4:3 the same man is unquestionably mentioned again under the name of Shisha, who is called Shavsha in the Chronicles, Sheva (שׁיא) in the text of 2-Samuel 20:25, and here Seraiah. Seraiah also is hardly a copyist's error, but another form for Shavsha or Shisha. The scribe was a secretary of state; not a military officer, whose duty it was to raise and muster the troops, for the technical expression for mustering the people was not ספר, but פּקד (cf. 2-Samuel 24:2, 2-Samuel 24:4,2-Samuel 24:9; 1-Chronicles 21:5-6, etc.).

Scribe - Or, secretary of state.