John Calvin Commentary Isaiah 30:21

"and thine ears shall hear a word behind thee, saying, This is the way, walk ye in it; when ye turn to the right hand, and when ye turn to the left." — Isaiah 30:21 (ASV)

Then shall thine ears hear. It was indeed no insignificant promise that He made concerning an abundant produce of the fruits of the earth, but the chief basis of gladness and joy is when God restores pure and sound doctrine to us.

For no scarcity of wheat should terrify and alarm us as much as a scarcity of the word; and indeed, just as the soul is more excellent than the body, so much more should we dread this kind of famine, as another prophet also reminds us (Amos 8:11).

Isaiah promises this to the Jews as the most valuable of all blessings: that they shall be fed with the word, the lack of which had formerly heavily afflicted them. The false prophets also boast of the word, and in a more haughty and disdainful manner than godly teachers. They wish to be considered and declared the best guides; but they lead people into error and eventually plunge them into destruction.

But the word that points out the right path comes from God alone, though it would be of little use to us if He did not also promise that He would give us ears; for otherwise He would speak to the deaf, and we would hear nothing but a confused sound.

A word behind thee. These words must be understood to mean that He will not permit what He speaks to us to be useless, but will inwardly move our understandings and hearts, so as to train them to true obedience. For by nature we are not willing to learn, and must be completely formed anew by His Spirit.

The word hear is very emphatic. He compares God to a schoolmaster, who places the children before His eyes, that He may more effectually train and direct them. By this He expresses the wonderful affection and care manifested towards us by God, who does not consider it enough to go before us, but also with His eye upon us gives us direction (Psalms 32:8), but the Prophet declares that those who follow God as their guide will be in no danger of going astray.

Walk ye in it. This is an exhortation to cheerful progress, so that their journey may not be hindered, as frequently happens, by any uncertainty.

What He adds about the right hand and the left might be thought absurd; for when Moses pointed out to the people the way in which they should walk, He at the same time charged them not to turn aside to the right hand or to the left (Deuteronomy 5:32; Deuteronomy 17:20). The road is straight, and we should not seek any departures from it.

What then does the Prophet mean? I reply, He uses the words Right and Left in a different sense, for He means by them every kind of transaction that we must undertake to perform. These are various, as there are also various modes of living; and every person meets with many kinds of difficulties and needs to deliberate about them.

By the right and left hand, therefore, He means all the actions of human life, whatever they are, so that, in all that we undertake, we may have God for our guide and may always regulate our transactions by His authority, whether we must go to the right hand or to the left. And from this we derive very great consolation: that the Lord will favor our undertakings and will direct our steps, to whatever hand we turn, provided only that we do not turn aside from the path which He points out to us.