SB 11.17.24

snāna-bhojana-homeṣu
 japoccāre ca vāg-yataḥ
na cchindyān nakha-romāṇi
 kakṣopastha-gatāny api
Word for word: 
snāna — while bathing; bhojana — while eating; homeṣu — and while attending sacrificial performances; japa — while chanting mantras to oneself; uccāre — while passing stool or urine; ca — also; vāk-yataḥ — remaining silent; na — not; chindyāt — should cut; nakha — the nails; romāṇi — or hairs; kakṣa — in the armpits; upastha — pubic; gatāni — including; api — even.
Translation: 
A brahmacārī should always remain silent while bathing, eating, attending sacrificial performances, chanting japa or passing stool and urine. He should not cut his nails and hair, including the armpit and pubic hair.
Purport: 

Nārada Muni gives a similar technical description of Vedic brahmacārī life in Canto Seven, Chapter Twelve, of Śrīmad-Bhāgavatam.