This fourth [chronological] question was put earlier. And first, indeed, St. Augustine and Abulensis (at the cited places) name a day of the third month. But [Augustine] will have it [reckoned] from the day of the slaying of the Lamb, and that [day] included — the fiftieth. Thus: on the 14th day of the first month the lamb was slain. From it, then, [it] included, there remain of the same month —— 16 days; of the second, 30; of the third, 3; [total] 49 [→ Pentecost the 50th]. But Abulensis and Rupert (at the cited place) [reckon] likewise from that same Passover day included — but because [the months were] lunar…
(col. 115)
…[because they use lunar] months, [and] say the day of the Law’s giving was indeed the third of the third month, but the 49th from that Passover. Thus: from the first month, days —— 15; [second] 29; [third] 6; [total] 50.
Scaliger (Isagoge of the Canons, book 3, ch. 6, p. 218) says, indeed, that the day of the Law and of Pentecost always falls on the sixth day of the third month; but he will have the first day counted between Passover and Pentecost be the [day] on which the sheaf of firstfruits was offered — that is, the 16th day of the first month — because, namely, he reckons the following second month to have been hollow, but not all the months equal, [as] most had been before the Exodus. But if the things disputed above are truer, then plainly it is welded together and made out — the very thing we seek — [that] it was the sixth day of the same third month, and, from the day of the Egyptian exodus (that not being counted as one), the 50th [from the 15th]. Thus: —— 15; 29; 6; [total] 50.
And more briefly thus. The day on which they were bidden to be ready against the third day, that they might receive the Law, was (as [was] said above, q. 8) the fourth of the third month, and the 48th from the exodus. Therefore the day of the Law’s own giving was the sixth of that month, and the 50th from the exodus. Because, as [was] proved in the same question, in the appointed triad of those days both the first and the third day are to be included, thus: — 1 | 48; 2 | 49; 3 | 50.
And this is the most received opinion of the other learned [men] — of Jerome, Cajetan, Ribera, Bellarmine (at the cited place) — and of all the Jews. But most inept [is] that [opinion] which, in [his] Tract. on Years (ch. 5, pp. 45, 46, 47), the Innovator Lydiat strives to bring in — yet without any good argument: [namely] that the sheaf of firstfruits was offered not on the day after the Passover, that is, the 16th day of the first month, but on the first day which, after the sabbath, should fall in the week of the unleavened bread — that is, always on that Lord’s day [Sunday], as we now speak in Christian [fashion], which either fell in that week of unleavened bread, or next followed it. But that it was a sabbath day on which the Law was given, Abraham Zacuth hands down (Yuhasin, fol. 9); and others, of whom [more] in ch. 2 of the Acts of the Apostles, q. 4.