What are works of mercy?
The Catechism defines the works of mercy as “charitable actions by which we come to the aid of our neighbor in his spiritual and bodily necessities.” 
You must do it for another’s good, without considering what you get out of it. Mercy is incompatible with self-interest.
Come to the aid:
You have to actually provide something they lack.
What good is it, my brothers, if someone says he has faith but does not have works? Can that faith save him? If a brother or sister has nothing to wear and has no food for the day,
and one of you says to them, “Go in peace, keep warm, and eat well,” but you do not give them the necessities of the body, what good is it? So also faith of itself, if it does not have works, is dead. (James 2:14-16)
This is a sticky point for some people. Some define “neighbor” so narrowly. It’s only a person I can see, a person who believes as I do, a person I deem deserving of aid, a person I like. Well, these qualifiers are nowhere to be found in the Catechism or Bible. They fly in the face of charity.
I define neighbor very broadly. In today’s age of globalization, spatial arbitrage, and the Internet, it’s a small small world. My definition of neighbor is anyone. Anyone at all. Gay homeless youth, persecuted Christians in the middle east, the lonely widow next door, are all my neighbors.
Where do works of mercy originate?
In a basic sense, works of mercy originate in natural law. It is written on the hearts of man to be charitable. Treat others as you wish to be treated.
In a specific sense, they also originate in Divine law.
Then the king will say to those on his right, ‘Come, you who are blessed by my Father. Inherit the kingdom prepared for you from the foundation of the world. For I was hungry and you gave me food, I was thirsty and you gave me drink, a stranger and you welcomed me, naked and you clothed me, ill and you cared for me, in prison and you visited me.’ (Matt. 25:34-36)
Who should perform works of mercy?
Because of the command given by Jesus, it is a scandal when Christians are outperformed by non-Christians. We all respond to the need of humanity out of natural law, the law written on our hearts. But Christians have a more urgent motive: obedience to Jesus’s instruction.
Instructing the ignorant, counseling the doubtful, and consoling the sorrowing are “not always within the competency of every one.” But most works of mercy, especially bearing wrongs patiently, forgiving offences willingly, and praying for the living and the dead require no special talents.
I am so excited to begin Mercy Mondays! I’ve been looking forward to sharing this weekly feature here on the blog. More details will be apparent next week, but here’s a general overview:
Monthly Theme and Challenge Ideas
Each month I will host an in-depth discussion on one of the works of mercy. Through sacred scripture, tradition, and magisterial documents, we will take a sweeping look at the historical understanding of each charitable work. Then, I will share how I am making an intentional, current practice of that work all month long, and challenge you to do the same!
Each Monday morning I will share an update on Books Faith Life. Some Mondays I will introduce a solid charity that focuses its efforts on the chosen month’s work of mercy. We will also discuss ways you can live out each work of mercy in your parish and home. I look forward to hearing from all of you in this as well!
Corporal and Spiritual Works of Mercy in the Catholic Encyclopedia
Corporal Works of Mercy at the USCCB
Spiritual Works of Mercy at the USCCB
Offer It Up! A Guide to Redemptive Suffering (here on Books Faith Life)