Too long have I had my dwelling
among those who hate peace.
I am for peace,
but when I speak, they are for war!
This is the first psalm labeled as "a song of ascents". That means is was used as a song of pilgrimage, sung by Jews as they journeyed to the temple for various feasts. This particular Psalm seems to capture the struggle a Jew would experience living in a far, pagan country, worshiping Yahweh and regularly returning to Jerusalem. The context makes it clear they are coming from among enemies of the Jews (Meshech and Kedar in Psalm 120:5) to worship in Jerusalem.
It appears the expectation for a Jew living among Gentiles was to make peace. In the song, the pilgrim is for peace even as the Gentiles talk war. Part of the longing to be back at the temple was for deliverance from this constant negativity marked by lies and hate (see Psalm 120:2-4). In the presence of God, in worship of God, peace could be known.
The "gospel of peace" as a New Testament phrase comes to mind immediately for me as I look for how this passage points to Jesus. Christ died and rose again so that sin could be atoned and peace with God made. Repenting of my sin, trusting Jesus, brings peace. If I too am to be for peace while sojourning in this world which is at war with God because of sin, then I must speak and live the gospel of peace... even if those who are bound by sin are at war with my holy God.