Blessed: see 1.3.

Those who wash their robes: see 7.14. Here nothing is said about “in the blood of the Lamb,” as in 7.14. It is implied, of course, that this washing makes the robes clean, and this may be expressly stated, “those who wash their robes clean” (Good News Translation). For robes see 6.11.

As the RSV footnote indicates, instead of who wash their robes, some Greek manuscripts have “who do his commandments” (see 12.17; 14.12). The text translated by Revised Standard Version and Good News Translation is to be preferred.

That: this appears to indicate purpose; and by placing a comma after robes, Revised Standard Version seems to connect that with Blessed. It is possible to take the Greek conjunction translated that to express purpose and connect it with the verbal phrase wash their robes: “those who wash their robes in order to….” But it seems better to take the conjunction as final, indicating result: “and as a result they have….” So New Revised Standard Version “so that they will have the right….”

Have the right to the tree of life: that is, have the right to eat the fruit of the tree (see 22.2).

Enter the city by the gates: this is somewhat strange, for it seems to imply that others will have to enter by some other way. The force of this statement may be what would be expressed in English by “the right to enter the city freely,” “full and free access to the city.” Since the tree of life is inside the city, it may be desirable to reverse the two actions as follows: “And so they will have the right to go through the gates into the city and eat the fruit from the tree of life.”

Quoted with permission from Bratcher, Robert G. and Hatton, Howard A. A Handbook on The Revelation to John. (UBS Handbook Series). New York: UBS, 1993. For this and other handbooks for translators see here .