It will have blood, they say, blood will have blood,
Stones have been known to move, and trees to speak;
Augurs, that understand relations, have
By magpies, and by choughs, and rooks, brought forth
The secret'st man of blood.—
In this passage the first line loses much of its force by the present punctuation. Macbeth having considered the prodigy which has just appeared, infers justly from it, that the death of Duncan cannot pass unpunished;
It will have blood:—
then, after a short pause, declares it as the general observation of mankind, that murderers cannot escape:
—they say, blood will have blood.
Murderers, when they have practised all human means of security, are detected by supernatural directions:
Augurs, that understand relations, &c.
By the word relation is understood the connexion of effects with causes; to understand relations as an augur, is to know how those things relate to each other, which have no visible combination or dependence.