SB 6.1.48

manasaiva pure devaḥ
 pūrva-rūpaṁ vipaśyati
anumīmāṁsate ’pūrvaṁ
 manasā bhagavān ajaḥ
Synonyms: 
manasā — by the mind; eva — indeed; pure — in his abode, or within everyone’s heart like the Supersoul; devaḥ — the demigod Yamarāja (dīvyatīti devaḥ, one who is always brilliant and illuminated is called deva); pūrva-rūpam — the past religious or irreligious condition; vipaśyati — completely observes; anumīmāṁsate — he considers; apūrvam — the future condition; manasā — with his mind; bhagavān — who is omnipotent; ajaḥ — as good as Lord Brahmā.
Translation: 
The omnipotent Yamarāja is as good as Lord Brahmā, for while situated in his own abode or in everyone’s heart like the Paramātmā, he mentally observes the past activities of a living entity and thus understands how the living entity will act in future lives.
Purport: 

One should not consider Yamarāja an ordinary living being. He is as good as Lord Brahmā. He has the complete cooperation of the Supreme Lord, who is situated in everyone’s heart, and therefore, by the grace of the Supersoul, he can see the past, present and future of a living being from within. The word anumīmāṁsate means that he can decide in consultation with the Supersoul. Anu means “following.” The actual decisions concerning the next lives of the living entities are made by the Supersoul, and they are carried out by Yamarāja.