SB 10.6.35-36

pūtanā loka-bāla-ghnī
 rākṣasī rudhirāśanā
jighāṁsayāpi haraye
 stanaṁ dattvāpa sad-gatim
kiṁ punaḥ śraddhayā bhaktyā
 kṛṣṇāya paramātmane
yacchan priyatamaṁ kiṁ nu
 raktās tan-mātaro yathā
Synonyms: 
pūtanā — Pūtanā, the professional Rākṣasī; loka-bāla-ghnī — who used to kill human children; rākṣasī — the she-demon; rudhira-aśanā — simply hankering for blood; jighāṁsayā — with the desire to kill Kṛṣṇa (being envious of Kṛṣṇa and having been instructed by Kaṁsa); api — still; haraye — unto the Supreme Personality of Godhead; stanam — her breast; dattvā — after offering; āpa — obtained; sat-gatim — the most elevated position of spiritual existence; kim — what to speak of; punaḥ — again; śraddhayā — with faith; bhaktyā — by devotion; kṛṣṇāya — unto Lord Kṛṣṇa; paramātmane — who is the Supreme Person; yacchan — offering; priya-tamam — the dearmost; kim — something; nu — indeed; raktāḥ — those who have an affinity; tat-mātaraḥ — Kṛṣṇa’s affectionate mothers (offering the beloved child their breasts); yathā — exactly like.
Translation: 
Pūtanā was always hankering for the blood of human children, and with that desire she came to kill Kṛṣṇa; but because she offered her breast to the Lord, she attained the greatest achievement. What then is to be said of those who had natural devotion and affection for Kṛṣṇa as mothers and who offered Him their breasts to suck or offered something very dear, as a mother offers something to a child?
Purport: 

Pūtanā had no affection for Kṛṣṇa; rather, she was envious and wanted to kill Him. Nonetheless, because with or without knowledge she offered her breast, she attained the highest achievement in life. But the offerings of devotees attracted to Kṛṣṇa in parental love are always sincere. A mother likes to offer something to her child with affection and love; there is no question of envy. So here we can make a comparative study. If Pūtanā could attain such an exalted position in spiritual life by neglectfully, enviously making an offering to Kṛṣṇa, what is to be said of mother Yaśodā and the other gopīs, who served Kṛṣṇa with such great affection and love, offering everything for Kṛṣṇa’s satisfaction? The gopīs automatically achieved the highest perfection. Therefore Śrī Caitanya Mahāprabhu recommended the affection of the gopīs, either in maternal affection or in conjugal love, as the highest perfection in life (ramyā kācid upāsanā vrajavadhū-vargeṇa yā kalpitā).