Its singular is zarbiyyah, according to all linguists and interpreters. Mabthūthah means spread out and unfurled.

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As for rafraf, al-Layth said: “It is a kind of green cloth spread out as a furnishing. Its singular is rafrafah.” Abū ‘Ubaydah said: “Rafārif means carpets,” and quoted Ibn Muqbil:

Indeed, we often alight where our sandals are covered
By trailing folds of wraps and carpets of every kind.

Abū Ishāq said: “It has been said that rafraf here means the meadows of Paradise. It has also been said to mean cushions, bedcovers, or the overhanging edges of bedcovers.”

Al-Mubarrid said: “It means the overhanging portions of fabrics that kings use for bedding and other purposes.”

Al-Wāhidī said: “This seems the likeliest interpretation, for the Arabs call the hanging side of a tent, and the piece of cloth attached along its lower edge, rafraf. Hence the report concerning the Prophet’s death, may Allah bless him and grant him peace: ‘He lifted the curtain, and we saw his face as though it were a sheet of paper.’ Ibn al-A‘rābī said: ‘Rafraf here means the edge of the tent.’ Thus, the portions of the bedcovers extending beyond what lies beneath them were likened to the edge of a tent and called rafraf.”

I say: The basic sense of this word relates to an edge or a side. Hence rafraf can mean a projecting ledge on a wall, the hanging side of a tent, or the sides of a coat of mail and the portions hanging down from it; the singular is rafrafah. From the same root, a bird is said to rafrafa when it flutters its wings around something, intending to land on it. Rafraf also means green fabrics used to make bedcovers; the singular is rafrafah. Anything that extends beyond something else and is folded or turned back is called rafraf.

In the hadith of Ibn Mas‘ūd concerning the words of Allah, Mighty and Majestic, “He certainly saw some of the greatest signs of his Lord,” he said: “He saw a green covering that filled the horizon.” This is recorded in both Sahīh collections.