Bhagavad Gita 12.5
But they who fix their attention on the Absolute and Impersonal encounter greater hardships, for it is difficult for those who have a body to realize Me as without one.
क्लेशोऽधिकतरस्तेषामव्यक्तासक्तचेतसाम्।
अव्यक्ता हि गतिर्दुःखं देहवद्भिरवाप्यते॥kleśo'dhikatarasteṣāmavyaktāsaktacetasām|
avyaktā hi gatirduḥkhaṃ dehavadbhiravāpyate||
English translation (above): Shri Purohit Swami (1935), public domain. Sanskrit text via github.com/gita/gita (Unlicense).