Found this at www.globalpsychics.com

The Right Day for Cutting

It seems that choosing a day to cut your hair or nails will bode for you in the following way:

Cut them on Monday, you cut them for health;
cut them on Tuesday, you cut them for wealth;
cut them on Wednesday, you cut them for news;
cut them on Thursday, a new pair of shoes;

cut them on Friday, you cut them for sorrow;
cut them on Saturday, see your true love tomorrow;
cut them on Sunday, the devil will be with you all the week.

There are a few variations on that rhyme, but in all circumstances, cutting on Sunday is cutting for evil.