Albert Barnes Commentary Judges 6:15

"And he said unto him, Oh, Lord, wherewith shall I save Israel? behold, my family is the poorest in Manasseh, and I am the least in my father`s house." — Judges 6:15 (ASV)

Gideon now perceived that the Lord was speaking to him by His angel. He saw, however, no qualifications in himself, or in his family or tribe, for the office of saviour to his people. He therefore desires some assurance that the message he had just received was indeed from God, and not a mere dream or delusion. He asks as a sign (Judges 6:18) that his mysterious visitor should wait under the oak until he should return to Him with his gifts and offerings.