Rashi on Exodus 18:15/רש"י על שמות י״ח:ט״ו

1כי יבא — This is the same as כי בא because the people comes”, the imperfect tense expressing continuous action.

2לדרש אלהים TO ENQUIRE OF GOD — Understand this as the Targum does: למתבע אלפן, to seek instruction from the mouth of the Almighty.