Matthew Poole and continuators on Revelation 15:2

2 And I saw as it were a sea of glass e mingled with fire f, and them that had gotten the victory over the beast, and over his image, and over his mark, and over the number of his name, standing on the sea of glass , having the harps of God .

for it is mentioned as the place of the glorified Saints, who had overcome all Temptations to Idolatry, either from Pagans (which were the best) or from Antichrist and his Party (which are called the Image of the Beast) and had avoided all kind of Compliance with them in Profession of the Religion which he would endeavour to impose upon them.

Harps of God signifie either the most excellent Harps, or holy Harps. Mr. Forbes saith well, they signifie Hearts tempered with Joy, and Love, and a grateful Sense of the Mercies of God towards them.

Marginal references: Chap. 5.8. & 14.2.