The ruling on one who says the closing salam once in the prayer

Finally, he asks about a number of matters and says: Is it permissible to say the closing salam once in the prayer? He means, is saying the closing salam once sufficient in the prayer? And is it sufficient in the iqamah (the second call) for a person to say, “The prayer has begun,” only once, or not? Please inform us; may Allah reward you.
Answer: What is preserved from the Prophet (peace and blessings be upon him) is two closing salams. The majority of the scholars held that one closing salam is sufficient and that it suffices. However, the correct and accurate view is that it is not sufficient, but rather two closing salams are necessary; because this is what is preserved from the Prophet (peace and blessings be upon him). He said: (peace and blessings be upon him). Therefore, it is obligatory for the imams and for others to say two closing salams. This is the relied-upon position.