Proclaim peace unto it - Interpreters are greatly divided concerning the objects of this law. The text, taken in connection with the context, (see Deuteronomy 20:15-18), appears to state that this proclamation or offer of peace to a city is only to be understood of those cities which were situated beyond the limits of the seven anathematized nations, because these latter are commanded to be totally destroyed. Nothing can be clearer than this from the bare letter of the text, unless some of the words, taken separately, can be shown to have a different meaning. For the common interpretation, the following reasons are given.

God, who knows all things, saw that they were incurable in their idolatry; that the cup of their iniquity was full; and as their Creator, Sovereign, and Judge, he determined to destroy them from off the face of the earth, "lest they should teach the Israelites to do after all their abominations," Deuteronomy 20:18. After all, many plausible arguments have been brought to prove that even these seven Canaanitish nations might be received into mercy, provided they,

1. Renounced their idolatry;

2. Became subject to the Jews; and,

3. Paid annual tribute: and that it was only in case these terms were rejected, that they were not to leave alive in such a city any thing that breathed, Deuteronomy 20:16.

then proclaim

2 Samuel 20:18-22 Then she spoke, saying, They were wont to speak in old time, saying, They shall surely ask counsel at Abel...

Isaiah 57:19 I create the fruit of the lips; Peace, peace to him that is far off, and to him that is near, said the LORD; and I will heal him.

Zechariah 9:10 And I will cut off the chariot from Ephraim, and the horse from Jerusalem, and the battle bow shall be cut off...

Luke 10:5,6 And into whatever house you enter, first say, Peace be to this house...

Acts 10:36 The word which God sent to the children of Israel, preaching peace by Jesus Christ: (he is Lord of all:)

2 Corinthians 5:18-21 And all things are of God, who has reconciled us to himself by Jesus Christ, and has given to us the ministry of reconciliation...

2 Corinthians 6:1 We then, as workers together with him, beseech you also that you receive not the grace of God in vain.

Ephesians 2:17 And came and preached peace to you which were afar off, and to them that were near.

Deuteronomy
Owing to the comparatively loose nature of the connection between consecutive passages in the legislative section, it is difficult to present an adequate summary of the book of Deuteronomy. In the first section, i.-iv. 40, Moses, after reviewing the recent history of the people, and showing how it reveals Jehovah's love for Israel, earnestly urges upon them the duty of keeping His laws, reminding them of His spirituality and absoluteness. Then follows the appointment, iv. 41-43--here irrelevant (cf. …
John Edgar McFadyen—Introduction to the Old Testament