What does scourge mean as it is used in the following lines from Act V, Scene 3 of Romeo and Juliet?

Prince: This letter doth make good the friar’s words,
Their course of love, the tidings of her death:
And here he writes that he did buy a poison
Of a poor ‘pothecary, and therewithal
Came to this vault to die, and lie with Juliet.--
Where be these enemies?--Capulet,--Montague,--
See what a scourge is laid upon your hate,
That Heaven finds means to kill your joys with love!

In this context, the word "scourge" means a punishment or source of affliction. The Prince is describing how the deaths of Romeo and Juliet, resulting from the feud between the Capulet and Montague families, serve as a punishment for their hatred and animosity towards one another.