Skandapurana 16.17.71

16.17.71

ketuṃ kṛṇveti ketuṃ vai satataṃ pūjayedbudhaḥ ..
bāhyataḥ pūrvataḥ śukraṃ dakṣiṇena yamaṃ tathā .. 71 ..

The wise man should constantly worship Ketu indeed with 'ketuṃ kṛṇvan'. / On the outside, Śukra in the east, and Yama in the south;