Albert Barnes Commentary Isaiah 3:10

"Say ye of the righteous, that [it shall be] well [with him]; for they shall eat the fruit of their doings." — Isaiah 3:10 (ASV)

Say you to the righteous - The meaning of this verse and the following is sufficiently plain, though commentators have given some variety of interpretation. They declare a great principle of the divine administration similar to what is stated in (Isaiah 1:19–20). Lowth reads it, ‘Pronounce you a blessing on the just; truly good (shall be to him).’

That it shall be well ... - The word rendered ‘well,’ means ‘good.’ The sense evidently is, that in the divine administration it shall be well to be righteous. The Septuagint has rendered this in a remarkable manner, connecting it with the previous verse: ‘Woe to their soul, for they take evil counsel among themselves, saying, ‘Let us bind the righteous, for he is troublesome to us:’ therefore, they shall eat the fruit of their doings.’

They shall eat ... - That is, they shall receive the appropriate reward of their works, and that reward shall be happiness. As a farmer who sows his field and cultivates his farm, eats the fruit of his labor, so shall it be with the righteous. A similar expression is found in (Proverbs 1:31):

Therefore shall they eat of the fruit of their own way,
And be filled with their own devices.

Also (Jeremiah 6:19): ‘I will bring evil upon this people, even the fruit of their thought;’ Compare to (Galatians 6:8).