Srimad Bhagavatam Canto 07, Chapter 12, Text 08

SB 7.12.8

kesa-prasadhanonmarda-
 snapanabhyañjanadikam
guru-stribhir yuvatibhih
 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
 brahmani raja-patnika
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.
Srimad Bhagavatam Canto 07, Chapter 12, Text 07
Srimad Bhagavatam Canto 07, Chapter 12, Text 09