Why are "esurivi" and "sitivi" used in perfect, but "hospes eram" in imperfect in the same context?

Question

There is a fragment of Gospel of Matthew (in Vulgata):

(...), esurivi enim et dedistis mihi manducare, sitivi et dedistis mihi bibere, hospes eram et collegistis me (...)

My question is: Why exactly are "esurivi" and "sitivi" used in perfect form, but "hospes eram" is used in imperfect?

From what I learned, perfect is used for the activities that took place at some point in the past and they are finished by now. On the contrary, imperfect is used to indicate the ongoing processes, which I think is more suitable for above use cases and is used in "hospes eram", but not in "sitivi" and "esurivi". Why is that?

Answer 1

In the Greek original of Mt 25, 35-36:

ἐπείνασα γάρ, καὶ ἐδώκατέ μοι φαγεῖν, ἐδίψησα, καὶ ἐποτίσατέ με, ξένος ἤμην, καὶ συνηγάγετέ με,

γυμνός, καὶ περιεβάλετέ με, ἠσθένησα, καὶ ἐπεσκέψασθέ με, ἐν φυλακῇ ἤμην, καὶ ἤλθετε πρός με

all the verbs are in the aorist tense, except for “I was”, which, in both of its occurrences, is imperfect (in the post-classical form ἤμην). The Latin version translates all the aorists with the Latin perfect (historically aorist/perfect), and the one imperfect verb with the Latin imperfect. So the real question is why the author of Matthew shifts tenses for this one word. I suspect that this is because in Greek the verb “to be” does not have a real aorist, but only the suppletive ἐγενόμην, which is perhaps too heavily laden with its etymological meaning “I became” to be an entirely satisfactory way to say “I was”.

Answer 2

Just to complement fdb's answer, the tense selection does not make the text grammatically wrong, but adds a nuance if read as it is written.

The imperfect is not necessarily ongoing now, but was ongoing in the past. Hence the difference with perfect may be nuanced, depending on the context.

As you say, it may denote an action that has not finished. But not necessarily: it may also -and primarily- express that the action was recurrent or continued, for a period of time, before it ended. In the first case, it is analogous to English 'used to' + (verb in infinitive). In the second case, it may be seen as similar to English's past continuous was/were + (verb) + -ing.

So hospes eram can be "literally" translated as I was being a foreigner/I used to be a foreigner, which in English may be better understood as I was a foreigner for a time or simply as I was a foreigner... (and you received me while I still was.)