There is a belief that hair cut during the waning moon grows more slowly.
There is a sign that even hair coloring is better done on the waxing moon: supposedly, the result is better and the dye lasts longer.
Where did the omen come from?
In ancient times, hair was endowed with semi-mythical properties. It was believed that it was a kind of connection between a person and the surrounding world. Therefore, in the old days, hair was treated with special reverence.
Ancestors either did not cut their hair or did it only at certain times. Women's hair was given special power. There was even a sign according to which men were supposed to comb their wives' hair before a fight in order to gain strength and luck from them.
What does the Moon have to do with it?
The Moon occupied a special place in the worldview of our ancestors. The Earth's satellite was associated with fertility. It was believed that everything multiplied during the waxing Moon. The opposite properties were attributed to the waning Moon.
Thus, the sign was born that one should not cut one's hair on the waning moon. The Slavs believed that not only would a person have to wait a long time for new hair to grow, but he would also lose some of his health.