This is an aphorism from my aphorism book.
어느 구름에서 비가 올지
eo·neu gu·reum·e·seo bi·ga ol·ji
which cloud-FROM rain-SUBJ come-FUTSPEC
[One doesn’t know] from which cloud the rain will come.
This wasn’t hard to understand, but I think there is something missing to make this an actual sentence. My grammar “bible” tells me that an ending such as “-ㄹ지” should come in a context such as “V-ㄹ지 모르다” [one doesn’t know V will happen]. I think the “doesn’t know” is missing but implied here. I didn’t know what to call the ending, so I labeled a “future speculative” – I have often struggled with what the “지” really is – it’s a kind of a “pre-negative” or subjunctive marker, in my linguistically semi-informed but Koreanically semi-ignorant view.