CC Ādi 4.42

dāsya, sakhya, vātsalya, āra ye śṛṅgāra
cāri prema, catur-vidha bhakta-i ādhāra
Word for word: 
dāsya — servitude; sakhya — friendship; vātsalya — parental affection; āra — and; ye — that; śṛṅgāra — conjugal love; cārī — four types; prema — love of God; catuḥ-vidha — four kinds; bhakta-i — devotees; ādhāra — the containers.
Translation: 
Four kinds of devotees are the receptacles of the four kinds of mellows in love of God, namely servitude, friendship, parental affection and conjugal love.