(I'm translating from the Spanish liturgical text for the first reading at mass)
"Open the gates that a just people will enter ...
"They keep peace because they trust in the Lord"
What I hear here is that only when we truly trust in the Lord can we forget our claims and even our needs, and thus live in peace, receive peace, and create peace.
It is not just Justice what is at the root of lasting Peace, because given our infinite desire -created to match our capacity for God- a desire that we experience as "nothing is enough", it will translate into a greediness that justice cannot hold back if our heart and our lives are not rooted firmly upon the Lord.
Let us pray today with the Psalm, Blessed are those who trust in the Lord". Let us pray for that trust for ourselves, but let us pray especially for our world in dire need of this kind of Peace -as we trust in the Lord.