This Mass is #21 in the 1998/2002 Lectionary for Mass, numbers 922 through 926. The world’s main monotheistic religions are big on orthopraxis, or right behavior, when it comes to charity and justice. There is no lack of good thematic material for this liturgy.
From the Jewish tradition, three choices: Mosaic Law reminds believers of providing for the needy (Deuteronomy 24:17-22), or there’s Job’s claim to charity (31:16-20, 24-25, 31-32), or Isaiah’s recount of God’s preferred fasting (58:6-11).
New Testament options are from Luke (Acts 11:27-30, where Paul and Barnabas deliver relief supplies) and Paul on generosity in 2 Corinthians (8:1-5, 9-15 or 9:6-15).
Four Gospel choices are solid, predictable, and suitable: the Last Judgment (Matthew 25:31-46), the miraculous feeding in Mark 6:34-44, inviting needy guests (Luke 14:12-14), or the parable of Lazarus and the rich man from the same gospel (16:19-31).
Looking at music, there’s no overlap in Psalm texts and antiphons for the propers and Liturgy of the Word. In the latter, Psalm 22B, a finale of rejoicing (23-24, 26-28, 31-32) or God a refuge for those in need (107:2-9), or praise for the virtuous believer (112:1-9).
Entrance Antiphon Psalm 74:20, 19
Look to your covenant, O Lord, and forget not the life of your poor ones for ever.
Communion Antiphon Matthew 11:28
Come to me, all who labor and are burdened, and I will refresh you, says the Lord.
Numerous Psalms come to mind that uphold justice for the poor and oppressed: 34, 50, 73 (not 74 so much), 85, 111, 112 (mentioned above), 128, and 146. Prophetic texts, even more so.
Some years ago, we blogged on Masses And Prayers For Various Needs And Occasions. In the GIRM, sections 368-378 cover the universal regulations on their use. You can check our brief comments here and here and here. The USCCB’s unannotated text on the matter is here.