How do you delete a contact for Samsung Galaxy s3?

Remove your SIM card. Then, insert it back into the phone. Your recent text contacts should be deleted.

Example- (Before removing SIM)

Menu>>Messaging>>Create Message>>

Composed Text: Hey!

Send To>>Recent Contacts>>

Bob/123456789

Suzy/123456789

Jack/123456789

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(After Removing SIM)

Menu>>Messaging>>Create Message>>

Composed Text: Hey!

Send To>>Recent Contacts>>

[Empty]

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I hope this helped! (: