Revelation 7:13-15

Young's Literal Translation

¹³ And answer did one of the elders, saying to me, `These, who have been arrayed with the white robes -- who are they, and whence came they?'

¹⁴ and I have said to him, `Sir, thou hast known;' and he said to me, `These are those who are coming out of the great tribulation, and they did wash their robes, and they made their robes white in the blood of the Lamb;

¹⁵ because of this are they before the throne of God, and they do service to Him day and night in His sanctuary, and He who is sitting upon the throne shall tabernacle over them;