CC Adi 3.21
apane na kaile dharma sikhana na yaya
ei ta siddhanta gita bhagavate gaya
“Unless one practices devotional service himself, he cannot teach it to others. This conclusion is indeed confirmed throughout the Gita and Bhagavatam.”
Bhakti Rasamrta Sindhu 1.1.11
anyabhilasita sunyam jnana karmadi anavrtam
anukulyena krsnanusilanam bhakti uttama
One should render [uninterrupted] transcendental loving devotional service exclusively for the pleasure of Lord Sri Krsna without any desire for material profit or gain through philosophical speculation or fruitive activities.
Any other desires or activities executed – such as looking to obtain money for our own materialistic purposes,looking for position, name/fame – which are outside of the realm of pure devotional service rendered exclusively for the pleasure of Krsna constitutes (compromised) devotional service mixed with other motive.
BG 11.54; 18.55
bhaktya tv ananyaya sakya aham evam vidho ‘rjuna
jnatum drastum ca tattvena pravestum ca parantapa
jnatum drastum ca tattvena pravestum ca parantapa
Only by undivided devotional service can I be understood as I am, standing before you, and can thus be seen directly. Only in this way can you enter into the mysteries of My understanding.
bhaktya mam abhijanati yavan yas casmi tattvatah
tato mam tattvato jnatva visate tad anantaram
tato mam tattvato jnatva visate tad anantaram
One can understand the Supreme Personality as He is only by devotional service. And when one is in full consciousness of the Supreme Lord by such devotion, he can enter into the kingdom of God.