That intercession is a great and necessary part of Christian devotion is very evident from scripture. The first followers of Christ seem to support all their love, and to maintain all their intercourse and correspondence, by mutual prayers for one another.

Saint Paul, whether he writes to churches or particular persons, shows his intercession to be perpetual for them, that they are the constant subject of his prayers. Thus to the Philippians, “I thank my God upon every remembrance of you, always in every prayer of mine for you all making request with joy” (Phil. 1:3–4). Here we see, not only a continual intercession, but performed with so much gladness, as shows that it was an exercise of love in which he highly rejoiced.

His devotion had also the same care for particular persons, as appears by the following passages: “I thank God, whom I serve from my forefathers, with a pure conscience, that without ceasing I have remembrance of thee in my prayers night and day” (2 Tim. 1:3). Apostles and great saints did not only thus benefit and bless particular churches, and private persons; but they themselves also received graces from God by the prayers of others. Thus saith Saint Paul to the Corinthians: “You also helping together by prayer for us, that for the gift bestowed upon us by the means of many persons, thanks may be given by many on our behalf” (2 Cor. 1:11).

This was the ancient friendship of Christians, uniting and cementing their hearts, not by worldly considerations, or human passions, but by the mutual communication of spiritual blessings, by prayers and thanksgivings to God for one another.

It was this holy intercession that raised Christians to such a state of mutual love, as far exceeded all that had been praised and admired in human friendship. And when the same spirit of intercession is again in the world, when Christianity has the same power over the hearts of people that it then had, this holy friendship will be again in fashion, and Christians will be again the wonder of the world, for that exceeding love which they bear to one another.

For a frequent intercession with God, earnestly beseeching him to forgive the sins of all mankind, to bless them with his providence, enlighten them with his spirit, and bring them to everlasting happiness, is the divinest exercise that the heart of man can be engaged in.

When therefore you have once habituated your heart to a serious performance of this holy intercession, you have done a great deal to render it incapable of spite and envy, and to make it naturally delight in the happiness of all.

This is the natural effect of a general intercession for all. But the greatest benefits of it are then received, when it descends to such particular instances as our state and condition in life more particularly require of us.

There is nothing that makes us love someone so much as praying for them.

Though we are to treat all people as neighbors, as any occasion offers; yet as we can only live in the actual society of a few, and are by our state and condition more particularly related to some than others; so when our intercession is made an exercise of love and care for those amongst whom our lot is fallen, or who belong to us in a nearer relation, it then becomes the greatest benefit to ourselves, and produces its best effects in our own hearts.

For there is nothing that makes us love someone so much as praying for them; and when you can once do this sincerely for anyone, you have fitted your soul for the performance of everything that is kind and civil towards them. This will fill your heart with a generosity and tenderness, that will give you a better and sweeter behavior than anything that is called fine breeding and good manners.

By considering yourself as an advocate with God for your neighbors and acquaintances, you would never find it hard to be at peace with them yourself. It would be easy for you to bear with and forgive those for whom you particularly implored the divine mercy and forgiveness.

If all people, when they feel the first approaches of resentment, envy, or contempt towards others; or if in all little disagreements and misunderstandings whatever, they should, instead of indulging their minds with little low reflections, have recourse, at such times, to a more particular and extraordinary intercession with God, for such persons as had raised their envy, resentment, or discontent; this would be a certain way to prevent the growth of all uncharitable tempers….

When at any time you find in your heart motions of envy towards any person, whether on account of his riches, power, reputation, learning, or advancement, if you should immediately betake yourself at that time to your prayers, and pray to God to bless and prosper him in that very thing which raised your envy; if you should express and repeat your petitions in the strongest terms, beseeching God to grant him all the happiness from the enjoyment of it, that can possibly be received; you would soon find it to be the best antidote in the world, to expel the venom of that poisonous passion.

This would be such a triumph over yourself, would so humble and reduce your heart into obedience and order, that the devil would even be afraid of tempting you again in the same manner, when he saw the temptation turned into so great a means of amending and reforming the state of your heart.

Again; if in any little difference, or misunderstandings that you happened to have at any time, with a relation, a neighbor, or anyone else, you should then pray for them in a more extraordinary manner than you ever did before; beseeching God to give them every grace, and blessing, and happiness, you can think of; you would have taken the speediest method that can be, of reconciling all differences, and clearing up all misunderstandings…. You cannot possibly have any ill temper, or show any unkind behavior to someone, for whose welfare you are so much concerned, as to be his advocate with God in private.

William Law, A Serious Call to a Devout and Holy Life (Grand Rapids, MI: Christian Classics Ethereal Library).