Can anybody help me with...

1. Which religions practise circumcision due to references in their texts and writings
2. What/where these references are specifically. It'd be great if you could post the reference, but if it's too long or you can't be bothered, a point in the general direction so I can look it up would be appreciated.

Please, I'm not after personal opinions/experiences at all, just some answers to the above questions.

Thanks so much.