Pause-on-hover is necessary when your images have a lot of detail, text that your users need to read, or have a specific call to action that you want them to make. Even if you don't have need of any of those things, it's still a good idea to add this functionality as it allows the user to get a good look at the images if they wish.
The following screenshot illustrates that the image rotation has stopped when the user hovered over the image:
To detect when we hover on and off our image rotator so that we can pause our image rotator, we need to add the following code to the line below image.eq(activeSlide).show();:
$("#slider").hover(function() {
clearInterval(timer);
}, function() {
timer = setInterval(rotate, speed);
});