Witchipedia

Spells rhyme for two reasons: to make them easier to remember and to add a musical quality to the words. Adding a musical quality adds another layer of energy and helps the person chanting and anyone listening to ease into a trance state.

The incantation part of a spell should state your intent and purpose very clearly and should be somewhat musical so that it can be chanted and assist in achieving an altered state of consciousness and to keep the focus on the intent. That is the goal and purpose of the incantation. You can achieve a musical feel to it by using rhythm, or rhyme or both or maybe neither if you've got some skill. Personally, I find rhythm to be most important. But whatever works for you, works!

I have seen some spells in some popular books with such horribly contrived rhymes that there's no way you could chant them without becoming distracted by their ridiculousness. If you can't make it rhyme without a huge stretch, it's my opinions that you just shouldn't!

A spl is a prayer and it can be said how ever you'd like. But I prefer to put time in to what I'm saying and the rhyme not only helps me get into Magickal state of mind it helps me remember them haha