SB 3.15.12

brahmovāca
mānasā me sutā yuṣmat-
 pūrvajāḥ sanakādayaḥ
cerur vihāyasā lokāl
 lokeṣu vigata-spṛhāḥ
Word for word: 
brahmā uvāca — Lord Brahmā said; mānasāḥ — born from the mind; me — my; sutāḥ — sons; yuṣmat — than you; pūrva-jāḥ — born previously; sanaka-ādayaḥ — headed by Sanaka; ceruḥ — traveled; vihāyasā — by traveling in outer space or flying in the sky; lokān — to the material and spiritual worlds; lokeṣu — among the people; vigata-spṛhāḥ — without any desire.
Translation: 
Lord Brahmā said: My four sons Sanaka, Sanātana, Sanandana and Sanat-kumāra, who were born from my mind, are your predecessors. Sometimes they travel throughout the material and spiritual skies without any definite desire.
Purport: 

When we speak of desire we refer to desire for material sense gratification. Saintly persons like Sanaka, Sanātana, Sanandana and Sanat-kumāra have no material desire, but sometimes they travel all over the universe, out of their own accord, to preach devotional service.