In the Vulgate (Acts 26:22-23), I came across the following:
...nihil extra dicens quam ea quæ prophetæ locuti sunt futura esse, et Moyses, si passibilis Christus, si primus ex resurrectione mortuorum, lumen annuntiaturus est populo et gentibus.
Both instances of the word si are translations of the Greek εἰ:
...οὐδὲν ἐκτὸς λέγων ὧν τε οἱ προφῆται ἐλάλησαν μελλόντων γίνεσθαι καὶ μωϊσῆς, εἰ παθητὸς ὁ χριστός, εἰ πρῶτος ἐξ ἀναστάσεως νεκρῶν φῶς μέλλει καταγγέλλειν τῶ τε λαῶ καὶ τοῖς ἔθνεσιν.
Although I would normally expect the translation for si and εἰ to be "if", in almost every translation into English I found for this verse, it is translated as "that" (and I agree that it makes the most sense for the context).
For example, the King James Version has:
...saying none other things than those which the prophets and Moses did say should come: That Christ should suffer, and that he should be the first that should rise from the dead, and should shew light unto the people, and to the Gentiles.
Can someone please elaborate on this usage of si (and perhaps of εἰ as well)?