Blessed are they that do his commandments. The Revised Version adopts the reading, οἱ πλύνοντες τὰς στολὰς αὐτῶν, "they that wash their robes," which is found in א, A, 1, 33, Vulgate, AEthiopic, Armenian, Primasius, and which is probably correct.
The reading of the Textus Receptus, ποιοῦντες τὰς ἐντολὰς αὐτοῦ, "they that do his commandments," is found in B, Syriac, Coptic, etc. The Vulgate adds, "in the blood of the Lamb," as in Revelation 7:14, which is, of course, the full meaning.
The free will of man is implied in the active form of the participle. That they may have right to the tree of life; in order that they may have authority over the tree of life; i.e. the right to partake of it.
Ebrard makes this clause dependent (as a consequence) upon "do:" "They do them in order that they may have," etc. Others attach this clause to "blessed: They are blessed because they may have the right," etc.
Both significations may well be implied. "The tree of life" is that described in Revelation 7:2, and promised "to him that overcometh" in Revelation 2:7. And may enter in through the gates into the city; by the portals; that is, in the natural way of people who have a right to enter.