On your walls, O Jerusalem, I have set watchmen;
all the day and all the night they shall never be silent.
You who put the LORD in remembrance, take no rest,
and give him no rest until he establishes Jerusalem and makes it a praise in the earth.
The LORD has sworn by his right hand and by his mighty arm:
"I will not again give your grain to be food for your enemies,
and foreigners shall not drink your wine for which you have laboured;
but those who garner it shall eat it and praise the Lord,
and those who gather it shall drink it in the courts of my sanctuary."
Barry Webb on these verses:
"[God] has a word of encouragement for all those who, like Isaiah, give themselves no rest but call on the LORD unceasingly to bring his plans for Zion to fruition. They are like watchmen whom God has set on Jerusalem's walls. He is the one who has raised them up as intercessors, and therefore they are licensed to be bold. They are to give the LORD himself no rest until his promise is fulfilled. The LORD is not offended by such bold intercession; it is precisely the kind of praying that he desires and commands.
"But there is a fine line, as we all know, between boldness and presumption. Boldness of the kind we are talking about here is justified only where prayer is based directly on the revealed will of God. That is why encouragement to be bold in verses 6 and 7 is followed immediately by a divine oath and a divine proclamation, in which the LORD's purposes are reaffirmed in the strongest possible terms.
"Rightly understood, there is tremendous encouragement in this passage for us in our praying, for so much of what Isaiah confidently expected is not happening. We live in the last great era of history. The promised Saviour has come to Zion, a banner has been raised for the nations by the worldwide proclamation of the gospel, and the final great pilgrimage has begun. If Isaiah had good reason to pray boldly for the fulfilment of God's promises concerning Zion, how much more do we! 'Father, may your kingdom come, may your will be done.'"
Webb, B. (1996) The Message of Isaiah (IVP), p.238-239