SB 11.18.43

brahmacaryaṁ tapaḥ śaucaṁ
 santoṣo bhūta-sauhṛdam
gṛhasthasyāpy ṛtau gantuḥ
 sarveṣāṁ mad-upāsanam
Synonyms: 
brahma-caryam — celibacy; tapaḥ — austerity; śaucam — purity of mind without attachment or repulsion; santoṣaḥ — full satisfaction; bhūta — toward all living entities; sauhṛdam — friendship; gṛhasthasya — of the householder; api — also; ṛtau — at the proper time; gantuḥ — approaching his wife; sarveṣām — of all human beings; mat — of Me; upāsanam — worship.
Translation: 
A householder may approach his wife for sex only at the time prescribed for begetting children. Otherwise, the householder should practice celibacy, austerity, cleanliness of mind and body, satisfaction in his natural position, and friendship toward all living entities. Worship of Me is to be practiced by all human beings, regardless of social or occupational divisions.
Purport: 

Sarveṣāṁ mad-upāsanam indicates that all followers of the varṇāśrama system must worship Lord Kṛṣṇa or risk falling down from their position. As stated in Śrīmad-Bhāgavatam (11.5.3), na bhajanty avajānanti sthānād bhraṣṭāḥ patanty adhaḥ: even though one may be advanced in the performance of Vedic rituals and customs, without worshiping the Supreme Lord one will certainly fall down.

Those in the householder āśrama are not authorized to enjoy life like pigs and dogs, freely exercising their sexual potency. A religious householder should approach his wife at the prescribed time and place and beget a saintly child for the pleasure of the Supreme Lord. Otherwise, it is specifically mentioned here that a householder must practice celibacy along with all of the other members of advanced human civilization. The word śaucam indicates cleanliness of mind and body, or else freedom from attachment and repulsion. One who faithfully worships God as the supreme controller experiences santoṣa, full satisfaction in whatever situation the Lord arranges. By seeing Lord Kṛṣṇa within everyone, one becomes bhūta-suhṛt, the well-wishing friend of all.