CC Madhya 23.23

vāgbhiḥ stuvanto manasā smarantas
tanvā namanto ’py aniśaṁ na tṛptāḥ
bhaktāḥ śravan-netra-jalāḥ samagram
āyur harer eva samarpayanti
Synonyms: 
vāgbhiḥ — by words; stuvantaḥ — offering prayers to the Supreme Personality of Godhead; manasā — by the mind; smarantaḥ — remembering; tanvā — by the body; namantaḥ — offering obeisances; api — although; aniśam — all the time; na tṛptāḥ — not satisfied; bhaktāḥ — the devotees; śravat — shedding; netra-jalāḥ — tears from the eyes; samagram — the whole; āyuḥ — life; hareḥ — to Kṛṣṇa; eva — only; samarpayanti — dedicate.
Translation: 
“ ‘With their words, they offer prayers to the Lord. With their minds, they always remember the Lord. With their bodies, they offer obeisances to the Lord. Despite all these activities, they are still not satisfied. This is the nature of pure devotees. Shedding tears from their eyes, they dedicate their whole lives to the Lord’s service.’
Purport: 

This verse from the Hari-bhakti-sudhodaya is found in the Bhakti-rasāmṛta-sindhu (1.3.29).