Srimad Bhagavatam Canto 03, Chapter 14, Text 20

SB 3.14.20

yam asrityendriyaratin
 durjayan itarasramaih
vayam jayema helabhir
 dasyun durga-patir yatha
 
Translationby His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
As a fort commander very easily conquers invading plunderers, by taking shelter of a wife one can conquer the senses, which are unconquerable in the other social orders.
 
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada: 
 
Of the four orders of human society — the student, or brahmacari order, the householder, or grhastha order, the retired, or vanaprastha order, and the renounced, or sannyasi 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 brahmacari, vanaprastha or sannyasi. Unless there is rigid and systematic training of the brahmacari by the expert spiritual master, and unless the student is obedient, it is sure that the so-called brahmacari will fall prey to the attack of sex. There are so many instances of falldown, even for great yogis like Visvamitra. A grhastha is saved, however, because of his faithful wife. Sex life is the cause of material bondage, and therefore it is prohibited in three asramas and is allowed only in the grhastha-asrama. The grhastha is responsible for producing first-quality brahmacaris, vanaprasthas and sannyasis.
Srimad Bhagavatam Canto 03, Chapter 14, Text 19
Srimad Bhagavatam Canto 03, Chapter 14, Text 21