Near the end of Stave 3 of A Christmas Carol, the Ghost of Christmas Present shows Scrooge a Christmas party hosted by Scrooge's nephew Fred. Fred's wife plays a song that was familiar with Scrooge's late sister Fan (Fred's mother):
Scrooge’s niece played well upon the harp; and played among other tunes a simple little air (a mere nothing: you might learn to whistle it in two minutes), which had been familiar to the child who fetched Scrooge from the boarding-school, as he had been reminded by the Ghost of Christmas Past. When this strain of music sounded, all the things that Ghost had shown him, came upon his mind; he softened more and more; and thought that if he could have listened to it often, years ago, he might have cultivated the kindnesses of life for his own happiness with his own hands, without resorting to the sexton’s spade that buried Jacob Marley.
Overall, the paragraph seems to be saying that Scrooge thinks that if he had listened to his sister's song more, he might have been more disposed to building a life filled with kindness, rather than the bitter miserly life he led. That said, I'm confused by the ending of the last line of this paragraph. What is meant by "without resorting to the sexton's spade that buried Jacob Marley"?
I get that a sexton's spade in this context would be a gravedigger's shovel. But the way it's phrased it makes it sound like burying Marley is in some way related to cultivating kindness. But that doesn't seem to make sense, so I'm not sure what the phrase is actually supposed to be saying.