svasyoddhavasya te’py eṣa kṛtvāhaṁ śapathaṁ bruve
svasyoddhavasya te’py eṣa kṛtvāhaṁ śapathaṁ bruve |
duḥsādhyaṁ tat-padaṁ hy atra tat-sādhanam api druvam ||
(Bṛhad Bhāgavatāmṛta: 2.5.208)
“Taking this oath before myself, Uddhava, and yourself, I say that here that domain [i.e., Goloka] is difficult to attain, and the means of attaining (sādhana) that certainly is as well.”