SB 3.14.20

Of the four orders of human society — the student, or brahmacārī order, the householder, or gṛhastha order, the retired, or vānaprastha order, and the renounced, or sannyāsī order — the householder is on the safe side. The bodily senses are considered plunderers of the fort of the body. The wife is supposed to be the commander of the fort, and therefore whenever there is an attack on the body by the senses, it is the wife who protects the body from being smashed. The sex demand is inevitable for everyone, but one who has a fixed wife is saved from the onslaught of the sense enemies. A man who possesses a good wife does not create a disturbance in society by corrupting virgin girls. Without a fixed wife, a man becomes a debauchee of the first order and is a nuisance in society — unless he is a trained brahmacārī, vānaprastha or sannyāsī. Unless there is rigid and systematic training of the brahmacārī by the expert spiritual master, and unless the student is obedient, it is sure that the so-called brahmacārī will fall prey to the attack of sex. There are so many instances of falldown, even for great yogīs like Viśvāmitra. A gṛhastha is saved, however, because of his faithful wife. Sex life is the cause of material bondage, and therefore it is prohibited in three āśramas and is allowed only in the gṛhastha-āśrama. The gṛhastha is responsible for producing first-quality brahmacārīs, vānaprasthas and sannyāsīs.