Peter Pett's Commentary on the Bible
Isaiah 51:7,8
God's Call To His People Not To Fear Men Or Their Reproaches Because They Will Fade Away While God's People Will Go On For Ever (Isaiah 51:7).
Again, for the third time, He stresses the importance of ‘listening'. They are to observe His instruction from their hearts. For those who have His instruction in their hearts need fear nothing, because they are not living in the light of this world, but of eternity. The world will pass away, but His word and His salvation will never pass away.
“Listen to me, you who know righteousness,
The people in whose heart is my instruction (law).
Do not fear the reproach of men,
Nor be dismayed at their revilings (virulent insults).
For the moth will eat them up like a garment,
And the worm will eat them like wool.
But my righteous deliverance (righteousness) will be for ever,
And my salvation to all generations.”
The fact that there are three calls emphasise the threefold completeness of the message. All are concerned with righteousness. In the first they are people who follow after righteousness and seek Yahweh (Isaiah 51:1). In the second His righteousness is near to come (Isaiah 51:5). Here in the third the hearers ‘know' righteousness. Thus His faithful people are in mind.
In the second His instruction went out to the nations to enlighten them, here He speaks to those in whose heart is His instruction. It may be that we are to see a progression from the people who look back to Abraham their father, to the nations who receive His instruction and light and come under His righteous jurisdiction, moving forward to a combination of these two as one people, conveying the idea of the reproach that they will face, and the triumph that will be theirs.
If that be so He addresses all His own as a people who know righteousness, they have heard it spoken of, they have come to an understanding of it, and they live it out in their experience. And through it they know the Righteous One. (To follow after righteousness is to seek Yahweh - Isaiah 51:1). For His instruction is within their hearts. They love His Law.
The command to them is then not to regard the reproaches of men ('enosh - weak and frail man), or their insults and vile words, for they are to recognise that the destiny of such people is to wear away, for like old clothing they will be eaten by moths and devoured by worms. In contrast the faithful will enjoy God's everlasting righteous deliverance, and a salvation that goes on and on and on. They will enjoy the everlasting kingdom.
Note again the similarities with 50. 6, 9. But while for the Servant in chapter 50 it was the present endurance that was in mind, here it is the reception of His word and of His instruction, and the future glory of His own, both Israel and the nations, that is emphasised. The work of the Servant has resulted in Israel turning to God and the nations receiving His light (Isaiah 49:6). His task is seen as fulfilled.