CC Ādi 3.104

tulasī-dala-mātreṇa
jalasya culukena vā
vikrīṇīte svam ātmānaṁ
bhaktebhyo bhakta-vatsalaḥ
Word for word: 
tulasī — of tulasī; dala — a leaf; mātreṇa — by only; jalasya — of water; culukena — by a palmful; vā — and; vikrīṇīte — sells; svam — His own; ātmānam — self; bhaktebhyaḥ — unto the devotees; bhakta-vatsalaḥ — Lord Kṛṣṇa, who is affectionate to His devotees.
Translation: 
“Śrī Kṛṣṇa, who is very affectionate toward His devotees, sells Himself to a devotee who offers Him merely a tulasī leaf and a palmful of water.”
Purport: 

This is a verse from the Gautamīya-tantra.