Hume is not saying that miracles are logically not possible. He is merely offering a check for the 'wise man' as to the validity of witnesses and their testimonies concerning the miraculous within the realm of sense-based experience. In Hume's official argument there is no attempt to rule out a priori the possibility of miracles taking place and at no point, not even during incautious over-statements of his position, does he ever rule out the legitimacy of believing what we see. There is the possibility of disbelieving something which may have happened. There can be no guarantees against deception, delusion and falsehood especially when the events occurred in an area of the world such where detection was inconceivable.
Miraculous narratives abound amongst 'primitive and barbarous people'.
Miracles are 'contrary facts' which cannot be reconciled without destroying one another. Thus, according to Hume's logic, Christianity is called to task on each of these four points as it was spread in a society where superstition was rife, and self-deception was common. The tombs broke open and the bodies of many holy people who had died were raised to life. Thus we might argue that the resurrection of Jesus is not a 'transgression of a law of nature ' in the sense that a resurrection is a unique event. The irony is that even if he did, his logic prevents him from stating this to be the case.