Forty, which Vatable dates from the time when the people petitioned for a king; Salien, from the first anointing of David. (Menochius)

It is probable enough that this number has been substituted instead of four, which Josephus, Theodoret, Syriac, Arabic, and many Latin manuscripts read; and Absalom would employ this term in securing the interest of Israel, before he declared himself openly their king. (Calmet)

He had been so long at Jerusalem, since his return. (Salien)

The canon of Hebrew verity, supposed to be made about the ninth century, is said (by Martinnay; Haydock) to be altered by some correcting hand, from four to forty. (Kennicott)

This is the famous Memmian canon, which Theodulph, bishop of Orleans, is believed to have ordered, as the standard of truth, according to the Hebrew copies of that day: (Haydock) and this seems to have guided the Ben. editor of St. Jerome’s works, and of his translation; so that it is no wonder if “the printed copies agree in so many places with the corrupted Hebrew.” Canon Memmianus purè leget juxta Hebræum, quod nos edidimus. (Note on 2 Paralipomenon xiii. 3, 17.) The Vulgate of Sixtus V, in that passage, as well as in the present, reads the smaller numbers, as he was guided by the best Latin copies, whereas Clement VIII has also consulted “the Hebrew fountains.” The former, says Kennicott, (Diss. ii. p. 205) “seems to have been printed on a juster plan....and the old Latin version is likely to be found more pure in the edition of Sixtus than in that of Clement, since the latter seems to have corrected his Latin by the modern (i.e., the corrupted) Hebrew copies.” Dr. James observes, that “almost all the Latin editions received in the Church, for many years, (preceding 1590) agree with Sixtus,” who here reads quatuor, with many others; so that Grotius is well supported in having pronounced so decisively, “without doubt there is a mistake, two letters having been added at the end of arbá. The thing itself declares that four years had elapsed.” (Kennicott)

It appears to be indubitable, that some mistakes have taken place with regard to numbers. But that this place is incorrect may not be so certain, as the chronology of Salien, Usher, &c., explains it well enough. The Hebrew text was esteemed more correct when the last editions of St. Jerome, and of the Vulgate, were given, than it is at present. (Haydock)