В души людям смотрят. gen.

[jarvisa]

From «Просьба» by Р. Рождественский:

Птицы, рыбы и звери
В души людям смотрят.

I am guessing:

Birds, fish and animals
Look into people's souls

but «людям» is not genitive so I assume this is incorrect.

What is the correct translation?

[redseasnorkel]

Look into human souls

http://answers.yahoo.com/question/index?qid=20111217104933AA5uDS9

[Francis Fanon]

When you say "do something to someone's something" in Russian, the person you're doing it to can be in the dative. Compare: пожать ему руку - "shake his hand"