Praying for the dead is one of the 7 spiritual works of mercy.
We lose nothing, dear brethren, by praying for them; be assured we are rather the gainers, for not only do they pray for us, but more— our charity towards them deepens in our souls our love for God, and makes us thirst the more after virtue and holiness, and wins for us a higher place in heaven and a brighter crown of everlasting glory. Transcript
Notes : In addition to the many partial and plenary indulgences available for specific good works (such as reading the bible for a half an hour, praying the rosary in front of the blessed sacrament etc.) There are also three general grants for indulgences that grant the faithful a partial indulgence either for their own sins or for the souls in purgatory they are
A partial indulgence is granted to the Christian faithful who, while performing their duties and enduring the difficulties of life, raise their minds in humble trust to God and make, at least mentally, some pious invocation.
A partial indulgence is granted to the Christian faithful who, prompted by a spirit of faith, devote themselves or their goods in compassionate service to their brothers and sisters in need.
A partial indulgence is granted to the Christian faithful who, in a spirit of penitence, voluntarily abstain from something which is licit for and pleasing to them. Norms for Indulgences 3rd Edition
Remember though, in order to gain an indulgence you have to have the intention of receiving one.
Eternal Rest Grant unto them O’Lord and let the perpetual light shine upon them. Amen
*This sermon was originally name the Communion of Saints but I changed the title sense it is focused on the Holy Souls in purgatory. On the transcript page you will find the source for this sermon which was written in the 1800s.
Original Image from a reprint of Un Catachisme en Images, Maision de la Bonne Press, 1909, derivative image work by AlleluiaAudioBooks.com