The Form of the Closing Salam of the Prayer

Question:
When the one who is praying finishes his prayer and wants to say the salam, should he say: "As-salamu alaykum wa rahmatullahi wa barakatuh" (Peace be upon you, and Allah's mercy and blessings) to the right and then to the left, or should he say: "As-salamu alaykum wa rahmatullahi" (Peace be upon you and Allah's mercy) only? And what is the ruling on the prayer of one who adds "wa barakatuh" (and blessings)?

Answer:
What is preserved in the Sunnah is "wa rahmatullahi" (and Allah's mercy) only, and this is what is prescribed: that one should say: "As-salamu alaykum wa rahmatullahi" (Peace be upon you and Allah's mercy) to his right and to his left. As for adding "wa barakatuh" (and blessings), there is disagreement among the scholars. 'Uqbah ibn Wail narrated from his father that the Prophet (peace and blessings be upon him) said it this way: "As-salamu alaykum wa rahmatullahi wa barakatuh" (Peace be upon you, and Allah's mercy and blessings). However, there is disagreement among the scholars regarding the validity of 'Uqbah hearing it from his father or not, and some of them said that it is a broken chain (munqati'). Therefore, what is prescribed for the believer is not to add it, but to restrict himself to: "wa rahmatullahi" (and Allah's mercy). If one adds it thinking it is correct, or being ignorant of the ruling, there is no blame on him, and his prayer is valid. However, the better and more cautious course is not to add it, in order to avoid the disagreement of the scholars and to act according to the most authentic and most cautious matter.