Furnished - Spread with carpets - εστρωμενον - so this word is often used. See Wakefield. But it may also signify the couches on which the guests reclined when eating. It does not appear that the Jews ate the passover now, as their fathers did formerly, standing, with their shoes on, and their staves in their hands.

Matthew 26:20 Now when the even was come, he sat down with the twelve.

Luke 22:14 And when the hour was come, he sat down, and the twelve apostles with him.

'Is it I?'
'Is it I?'--Mark xiv. 19 The scene shows that Judas had not as yet drawn any suspicion on himself. Here the Apostles seem to be higher than their ordinary stature; for they do not take to questioning one another, or even to protest, 'No!' but to questioning Christ. I. The solemn prophecy. It seems strange at first sight that our Lord should have introduced such thoughts then, disturbing the sweet repose of that hallowed hour. But the terrible fact of the betrayal was naturally suggested by the emblems …
Alexander Maclaren—Expositions of Holy Scripture

Questions About the Lord's Supper
THE paper which begins at this page requires a few words of prefatory explanation. It consists of fifty-one questions about the Lord's Supper, with special reference to points which are the subject of much dispute and controversy in the present day. It supplies fifty-one answers to these questions, chiefly drawn from the New Testament, and the Articles, Communion Service, and Catechism of the Church of England. It contains, in addition, some valuable extracts from the writings of standard English …
John Charles Ryle—The Upper Room: Being a Few Truths for the Times

That He who is About to Communicate with Christ Ought to Prepare Himself with Great Diligence
The Voice of the Beloved I am the Lover of purity, and Giver of sanctity. I seek a pure heart, and there is the place of My rest. Prepare for Me the larger upper room furnished, and I will keep the Passover at thy house with my disciples.(1) If thou wilt that I come unto thee and abide with thee, purge out the old leaven,(2) and cleanse the habitation of thy heart. Shut out the whole world, and all the throng of sins; sit as a sparrow alone upon the house-top,(3) and think upon thy transgressions …
Thomas A Kempis—Imitation of Christ