Many are surprised that the “Edit” button in Messages app is gone in iOS 7. The button was at the right top corner of message window and was used to delete unwanted text message.
To delete text messages in Messages app in iOS 7, first tap and hold on a message to pop up a menu. Tap on the menu option “More…” to bring out the edit window. You can then tap on the check circle to select more messages, and tap the trash icon at bottom left to remove your selected messages. To quickly remove all messages, tap the “Delete All” button at left top corner.