Jñāneśvarī (commentary on the Bhagavadgītā) 4.143

4.143

heṃ arjunā sakaḷa kuvāḍeṃ |
je anuṣṭhitāṃ atisāṃkaḍe |
parī jiteṃdriyāsīci ghaḍe |
yogyatāvaśeṃ ||

All this, O Arjuna, is difficult, / and very arduous when undertaken; / yet it is accomplished only by one who has conquered the senses, / by virtue of his fitness.