In this excerpt, we see Martin encountering a funeral procession and demonstrating his exceptional power over people, even if he did so by mistake.
It happened later, while he was on a journey, he encountered the body of a certain pagan which was being carried to a tomb with superstitious funeral rites. Seeing the crowd of those accompanying it, he stood aside, not knowing what was happening. Since he was half a mile off, it was difficult to distinguish what he saw. (2)Nevertheless, because he saw the rustic company and the linen cloth thrown over the body fluttering about as the wind was blowing it, he thought that an unholy rite of sacrifices was being performed. It was the custom of Gallic rustics to carry around the image of demons, covered in a shroud in a miserable madness. (3)Lifting the sign of the cross against them, he ordered the mob not to move from the place and they should set aside their burden. Here, in an astonishing way, you would see that they stood still at first just as rocks. (4)Then, when they were struggling to move forward with the utmost effort, they were able to accomplish nothing more than to whirl around in a ridiculous circle, until, beaten, they set aside the burden of the body. Astonished and looking at each other in turn, they silently thought about what had happened to them then. (5) When that blessed man discovered that it was the throng of a funeral procession, not of accursed (gods), raising his hand again, he gave them the power to leave and to raise the body. Thus, when he wished them to stand, he compelled them to do so. When it was pleasing, he allowed them to leave.
The first thing to note here is that this passage is continuing the theme of suppressing the rural pagan practices that were characteristic in St. Martin's Gallic setting. Here he is isn't even seeking out a confrontation, but, in a chance encounter, he seeks to confront what he thinks is a pagan religious procession in action. This should emphasize how important this activity was for Martin, whose fame rests, in a large part, on his efforts to Christianize the countryside around Tours; an effort which was incomplete throughout the Western Empire. The countryside was notoriously slow to adopt Christianity and much of Martin's activities was concentrated on this effort.
Second, we have to deal with what is actually happening here. What St. Martin thinks he's dealing with is a sacred procession in which a god is carried around the countryside, possibly for fertility rites, possibly as protection against death. I lean a little towards the second because the confusion with the funeral rites may suggest that a chthonic deity is meant here. Still, given the close link between underworld gods and fertility gods, I don't think this is a given. The similarities in the rites are interesting.
Third, we see another demonstration of St. Martin's powers in the vain struggle of the people in the procession to proceed. The almost funny spectacle of the members of the funeral procession whirling around in circles is a vivid image, but it demonstrates St. Martin's power (through the grace of God) to control the outside world and people. This continues the theme of wonder-working that we've already seen in St. Martin's story and will continue to follow it as we go.
As a query, I wonder if there is a biblical or patristic story about a prophet or holy man halting a procession like this. I can't recall anything that is really close.