And there were many lights - Why this circumstance is mentioned is not apparent. It, however, meets one of the slanders of the early enemies of Christianity, that the Christians in their assemblies were accustomed to extinguish all the lights, and to commit every kind of abomination. Perhaps the mention of many lights here is designed to intimate that it was a place of public worship, as not only the Jews, but the Gentiles were accustomed to have many lights burning in such places.
In the upper chamber - See the notes on Acts 1:13.

Upper chamber - It was in an upper chamber in the temple that the primitive disciples were accustomed to meet: on that account, they might have preferred an upper chamber whenever they could meet with it. The pious Quesnel supposes that the smoke, issuing from the many lamps in this upper chamber, was the cause of Eutychus falling asleep; and this, he says, the apostle mentions, in charity, to excuse the young man's appearing negligent.

(4) And there were many lights in the upper chamber, where they were gathered together.
(4) The devil, taking care to trouble the Church with a great offence, gives Paul a singular occasion to confirm the Gospel

And there were many lights in the upper chamber,.... Which were lighted up, both for necessary uses, to see by, to read the word, and to administer the ordinance of the supper, and for the comfort and pleasure of the whole company, both preacher and hearers; as well as to remove all ground of suspicion, or occasion of reproach, as if it was a midnight society met for wicked practices: but this no ways countenances the use of lamps and wax candies in the daytime at divine worship, since this was in the night; of the upper chamber, in which it was usual to meet for religious exercises, see Mark 2:4, where they were gathered together; the Alexandrian copy, Vulgate Latin, Syriac, and Arabic versions read, "where we were gathered together".

there were many lights in the upper chamber--not a mere piece of graphic detail by an eye-witness [HACKETT, HOWSON], but mentioned, probably, as increasing the heat and contributing to drowsiness [WEBSTER and WILKINSON], as the next clause seems to show.

There were many lamps in the room where they were assembled - To prevent any possible scandal.