I want to share with you a letter I received last week. It said, ‘When my mother separated from her husband, in the 1940s, she had to set up a home for herself and two daughters, with very little money. In her papers I discovered that St Martin-in-the-Fields had given her help at that time, and I am most grateful for that. I saw your article in the Church of Scotland magazine and thought that this would be an appropriate time to make a grateful donation towards helping someone else in difficulties.’

There’s a popular expression ‘What goes around, comes round.’ It’s urban slang for, ‘You reap what you sow.’ But in my experience the phrase is invariably used negatively, as a warning, a lesson drawn from a cautionary tale. Thomas a Kempis puts it more positively: ‘Whatsoever is done out of pure love, be it ever so little or contemptible in human sight, is wholly fruitful; for God measures more with how much love you work, than the amount you do.’

There’s a simple lesson we can draw from this: never underestimate the amount of good one humble kind word or deed can do. But there’s a more significant lesson that goes further. Goodness is more infectious than evil. St Augustine teaches us that in the end what’s wrong with evil is that it won’t finally exist – it is of no lasting purchase or value. Good, on the other hand, is a token or a signifier of what will last forever.

We often worry that if people we care for keep the wrong company, they’ll fall into bad ways. But the inspiring thing about the Scottish story and about Thomas a Kempis’ words is this: it’s not evil that’s infectious, it’s good. A good deed or gesture is like a mark in indelible ink: once made, it can never be eradicated. It’s written in the blood of Christ.

Revd Dr Sam Wells