Albert Barnes Commentary Isaiah 50:9

"Behold, the Lord Jehovah will help me; who is he that shall condemn me? behold, all they shall wax old as a garment, the moth shall eat them up." — Isaiah 50:9 (ASV)

The Lord God will help me - . In the Hebrew this is, ‘The Lord Jehovah,’ as it is in Isaiah 50:7 also, and these are among the places where our translators have improperly rendered the word יהוה yehovah (Jehovah) by the word ‘God.’

Who is he that shall condemn me? - If Yahweh is my advocate and friend, my cause must be right. Similar language is used by the apostle Paul: If God be for us, who can be against us? (Romans 8:31); and in Psalm 118:6:

Jehovah is on my side; I will not fear:
What can man do unto me?

They all shall wax old - All my enemies will pass away, as a garment is worn out and cast aside. The idea is that the Messiah would survive all their attacks; his cause, his truth and his reputation would live, while all the power, the influence, the reputation of his adversaries, would vanish as a garment that is worn out and then thrown away. The same image respecting his enemies is used again in Isaiah 51:8.

The moth shall eat them up - The moth is a well-known insect that particularly infests woolen clothes and soon consumes them (see the note at Job 4:19). In eastern countries, where wealth largely consisted of changes of clothing, the damage caused by moths would be particularly feared, and for this reason, it is frequently mentioned in the Bible. The meaning here is that the adversaries of the Messiah would be completely destroyed.