karayen natmano yuva
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
If the wife of the spiritual master is young, a young brahmacari should not allow her to care for his hair, massage his body with oil, or bathe him with affection like a mother.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The relationship between the student or disciple and the wife of the spiritual master or teacher is like that between son and mother. A mother sometimes cares for her son by combing his hair, massaging his body with oil, or bathing him. Similarly, the wife of the teacher is also a mother (guru-patni), and therefore she may also care for the disciple in a motherly way. If the wife of the teacher is a young woman, however, a young brahmacari should not allow such a mother to touch him. This is strictly prohibited. There are seven kinds of mothers:
atma-mata guroh patni
dhenur dhatri tatha prthvi
saptaita matarah smrtah
These mothers are the original mother, the wife of the teacher or spiritual master, the wife of a brahmana, the king’s wife, the cow, the nurse and the earth. Unnecessary association with women, even with one’s mother, sister or daughter, is strictly prohibited. This is human civilization. A civilization that allows men to mix unrestrictedly with women is an animal civilization. In Kali-yuga, people are extremely liberal, but mixing with women and talking with them as equals actually constitutes an uncivilized way of life.