Bhagavatapurana 4.12.30

4.12.30

tadottānapadaḥ putro dadarśāntakam āgatam /
mṛtyor mūrdhni padaṃ dattvā ārurohādbhutaṃ gṛham //

30. Then (at that moment) the son of Uttānapāda saw Yama approach him; and having set his foot on his (Yama's) head (i. e. triumphing over death) mounted into that wonderful car. (Here the commentator tells the story thus:—When Dhruva was about to mount the car, Yama came up and requested that he might be received; and Dhruva welcomed him and asked him to stop a while, contemplated Vishnu and actually setting his foot on the head of Yama, he mounted the car).