KAṬHA UPANISHAD · 2.2.12

एको वशी सर्वभूतान्तरात्मा
एकं रूपं बहुधा यः करोति ।
तमात्मस्थं येऽनुपश्यन्ति धीराः
तेषां सुखं शाश्वतं नेतरेषाम् ॥ १२॥

eko vaśī sarvabhūtāntarātmā
ekaṃ rūpaṃ bahudhā yaḥ karoti ।
tamātmasthaṃ ye’nupaśyanti dhīrāḥ
teṣāṃ sukhaṃ śāśvataṃ netareṣām ॥ 12॥

One calm and controlling Spirit within all creatures that maketh one form into many fashions; the calm and strong who see Him in the self as in a mirror, theirs is eternal felicity and ’tis not for others.