What is said when offering condolences to a Muslim, and what is their response?

It is sunnah to offer condolences to the deceased's family and to encourage them to be patient with Allah's decree. This can be done with any wording that conveys the purpose. The best wording is the Prophet's (peace be upon him) saying: "Indeed, to Allah belongs what He has taken and to Him belongs what He has given, and everything with Him has an appointed term. So be patient and seek reward." There is no objection to other phrases such as: "May Allah magnify your reward" or "May Allah improve your solace." It is good for the one being consoled to respond by supplicating for the consoler, such as: "May Allah reward you with good."