Skandapurana 1.4.39.168

1.4.39.168

dharmato dhanamāhārya yaṣṭavyaṃ cāpi yatnataḥ..
hīnebhyopi na yuṃjīta tvaṃkāraṃ karhicidbadhaḥ..
tvaṃkāro vā vadho vāpi gurūṇāmubhayaṃ samam.. 41.168 ..

Wealth should be acquired righteously, and one should also sacrifice with effort.
A wise man should never address even an inferior with 'thou';
addressing with 'thou' or slaying—both are equal in the case of gurus.