CC Antya 20.79

ākāśa — ananta, tāte yaiche pakṣi-gaṇa
yāra yata śakti, tata kare ārohaṇa
Synonyms: 
ākāśa — the sky; ananta — unlimited; tāte — in that sky; yaiche — just as; pakṣi-gaṇa — all types of birds; yāra — of someone; yata śakti — whatever power; tata — that much; kare ārohaṇa — rises up and up.
Translation: 
The sky is unlimited, but many birds fly higher and higher according to their own abilities.