The phrase "came on" means that Yahweh's Spirit influenced Samson. In this case, he made him very strong. Alternate translation: "Yahweh's Spirit made him very strong" (See: [[rc://en/ta/man/translate/figs-idiom]])
Here it states that he had nothing in his hand to emphasize that he was not holding a weapon. Alternate translation: "did not have a weapon" (See: [[rc://en/ta/man/translate/figs-litotes]])