The Feet of the Gospel of Peace is part of the armor of God as described in Ephesians 6:10-20 by Apostle Paul to the Church at Ephesus. This is a spiritual armour which gives us an illustration of how we ought to give feet to the Gospel of Peace. When we have our eyes fixed on our Lord Jesus by constantly reading the Bible, wherever there is an opportunity presented by the Lord to proclaim the Gospel to either our families, friends, or even to strangers, we would be able to do so. This way we give feet to the Gospel. The Bible says:
"How beautiful upon the mountains are the feet of him that bringeth good tidings, that publisheth peace; that bringeth good tidings of good, that publisheth salvation; that saith unto Zion, Thy God reigneth!" - Isaiah 52:7
It is not possible to give feet to the Gospel of Peace without the other two armour, namely the loincloth of truth and the breastplate of righteousness, because unless our foundation in the Gospel is strong, we would not be able to proclaim the Gospel effectively. Every piece of the armor of God complements each other, and the armour depicts a Christ centered lifestyle. When people look at our lifestyle centered in Christ and question us regarding our faith, this gives us an opportunity to proclaim the Gospel of Peace. Apostle Paul calls us as a living epistle or letter in Christ:
"Forasmuch as ye are manifestly declared to be the epistle of Christ ministered by us, written not with ink, but with the Spirit of the living God; not in tables of stone, but in fleshy tables of the heart" - 2 Corinthians 3:3
Our lifestyle being Christ centered and us being a living epistle in Christ, is the fruit of our faith rooted in Christ. This is the reason Apostle Paul starts describing the armor of God starting with the loincloth of truth followed by the breastplate of righteousness. The feet of the Gospel of Peace points to our actions as a fruit of our saving faith in Christ Jesus.
The Gospel proclaims the righteousness of God. If you are hearing a gospel that is proclaiming the sinfulness of man, or the judgment of God, then it is a clear indication that you are hearing a different gospel than the one Apostle Paul preached. The Bible says:
"To declare, I say, at this time his righteousness: that he might be just, and the justifier of him which believeth in Jesus" - Romans 3:26
Whenever people heard Apostle Paul preach The Gospel, they became conscious of their abundant forgiveness in Christ Jesus, which resulted in people repenting and turning to Christ. It is called the Gospel of Peace because, even though hearing the Gospel convicts a person of their sins, it assures them of their abundant forgiveness in Christ's one time and eternal sacrifice on the cross, which keeps their conscious clear that their sins have been forgiven righteously. Apostle Paul while proclaiming the Gospel said the following which made the Jews angry on the next day when they saw the multitude of people who were interested in hearing the Gospel:
"Be it known unto you therefore, men and brethren, that through this man is preached unto you the forgiveness of sins: And by him all that believe are justified from all things, from which ye could not be justified by the law of Moses" - Acts 13:38-39
The Gospel always points to the death, burial and resurrection of Christ, thus pointing to the Cross and mentioning the Blood of Christ. The Gospel can never be preached without mentioning the Cross or the Blood of Christ. Apostle Paul did warn the Church at Galatia to be very careful and pronounced a curse on the people or an angel preaching a different gospel other than the one that Apostle Paul preached:
"But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed" - Galatians 1:8
In the book of Acts, when the prison guard asked Apostle Paul and Silas as to what he must do to be saved, they replyed saying:
"...Believe on the Lord Jesus Christ, and thou shalt be saved, and thy house" - Acts 16:31
When some false believers had infiltrated into the Church and added circumcision to the Gospel Apostle Paul got furious. Apostle Peter was behaving differently with the Gentiles just because they were uncircumcised and he began to withdraw himself from the Gentiles as seen in Galatians 2. Some Jews also joined Apostle Peter in this and because of which even Barnabus was let astray from the original Gospel. Apostle Paul rebuked Apostle Peter in front of all of them in Antioch for trying to preach a different gospel by adding the law of circumcision as seen in Galatians 2:14 onwards. Apostle Paul says:
"Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified" - Galatians 2:16
The first century Christians were people who were led by the Apostles rooted in God's Word and full of the Holy Spirit. They had a zero tolerance policy for any traditions or practices that were outside of scripture. These people held on to the truth where their feet were always shod with the preparation of the Gospel of peace.