The cause of a thing's existing in time is the cause of its having been future from eternity, as of its being past for ever
So whatever causes a thing to exist at some point in time is exactly what causes it to have been going to exist from eternity. In the same way, whatever is the cause of a thing's having been at some time is the cause of its being called past for ever.
A cause existing from eternity is no more needed for a thing to have been future from eternity than a cause lasting for ever is needed for a thing to be past for ever. A future cause is enough for a future effect, just as a past cause is enough for a past one.
Latin
LVII. Igitur quod est causa cur res in tempore aliquando existat, idem plane causa est cur res ab aeterno extitura fuerit. Sicut quod causa est cur res aliquando fuit, causa est cur in aeternum dicetur praeterita. Nec magis requiritur causa ab aeterno existens, ut res ab aeterno futura fuerit, quam requiritur causa in aeternum duratura, ut in aeternum res praeterita sit. Ad effectum futurum sufficit causa futura, sicut ad praeteritum sufficit causa praeterita.