The basic principle of spiritual life

If a butter pot and fire are kept together, the butter within the pot will certainly melt. Woman is compared to fire, and man is compared to a butter pot. However advanced one may be in restraining the senses, it is almost impossible for a man to keep himself controlled in the presence of a woman, even if she is his own daughter, mother or sister. Indeed, his mind is agitated even if one is in the renounced order of life. Therefore, Vedic civilization carefully restricts mingling between men and women. If one cannot understand the basic principle of restraining association between man and woman, he is to be considered an animal.

Srimad Bhagavatam 7.10.9 purport