A.T. Robertson Commentary Luke 19:42

"saying, If thou hadst known in this day, even thou, the things which belong unto peace! but now they are hid from thine eyes." — Luke 19:42 (ASV)

If thou hadst known (ε εγνως). Second aorist active indicative of γινωσκω. Secondclass condition, determined as unfulfilled.

Even thou (κα συ). Emphatic position of the subject.

But now (νυν δε). Aposiopesis. The conclusion is not expressed and the sudden breaking off and change of structure is most impressive.

They are hid (εκρυβη). Second aorist passive indicative of κρυπτω, common verb, to hide.