Greek: o de parakupsas (AAPMSN) eis nomon teleion ton tes eleutherias kai parameinas, (AAPMSN) ouk akroates epilesmones genomenos (AMPMSN) alla poietes ergou, houtos makarios en te poiesei autou estai. (3SFMI)
Amplified: But he who looks carefully into the faultless law, the [law] of liberty, and is faithful to it and perseveres in looking into it, being not a heedless listener who forgets but an active doer [who obeys], he shall be blessed in his doing (his life of obedience). (Amplified Bible - Lockman)
ASV:  But he that looketh into the perfect law, the law of liberty, and so continueth, being not a hearer that forgetteth but a doer that worketh, this man shall be blessed in his doing.
KJV:  But whoso looketh into the perfect law of liberty, and continueth therein, he being not a forgetful hearer, but a doer of the work, this man shall be blessed in his deed.
NLT:  But if you keep looking steadily into God's perfect law—the law that sets you free—and if you do what it says and don't forget what you heard, then God will bless you for doing it. (NLT - Tyndale House)
Phillips: But the man who looks into the perfect mirror of God's law, the law of liberty (or freedom), and makes a habit of so doing, is not the man who sees and forgets. He puts that law into practice and he wins true happiness.  (Phillips: Touchstone)

BUT ONE WHO LOOKS INTENTLY AT THE PERFECT LAW, THE LAW OF LIBERTY, AND ABIDES BY IT: o de parakupsas (AAPMSN) eis nomon teleion ton tes eleutherias kai parameinas, (AAPMSN):

But (1161) (de)

One who looks intently (3879 ) (parakupto)

At (1519) (eis)

Perfect (5046) (teleios)

Law (3551) (nomos)

Liberty (1657)

Abides (3887)

NOT HAVING BECOME A FORGETFUL HEARER BUT AN EFFECTUAL DOER: ouk akroates epilesmones genomenos (AMPMSN) alla poietes ergou:

Not (3756) (ou)

Having become (1096)

Hearer (202) (akroates)

Forgetful (1953)

But (235)

Effectual (of work) (2041)

Doer (4163)

Spurgeon writes that...

There are many who complain of their short memories when they are hearing sermons. Well, then, let them be quick about doing what the sermon bids them, and then they will not be forgetful hearers. You have heard how one good woman described the effect of the sermon she has heard. She was one who washed wool, and when her minister went round to ask her what she had learned on the previous Sabbath, she did not even recollect the text. “Oh, Janet!” said he, “I am afraid you are a forgetful hearer; I cannot see what good the sermon has done to you.” So she took him to the back of her house, where she had a pump; and she worked at the handle while she held underneath the spout a sieve full of wool that was dirty and foul. The water ran through the wool, and through the sieve, and all ran away. “There,” she said, “this sieve is like my memory; but, sir, though the water does not stop in the sieve, it washes the wool; and what you preach, though it does not stop in my memory, it has washed my heart and cleansed my life and conversation.” Never mind about keeping the water in the sieve so long as it washes the wool. No man can be said to be a forgetful hearer who is a doer of the work that he is bidden to perform.

THIS MAN WILL BE BLESSED IN WHAT HE DOES: houtos makarios en te poiesei autou estai. (3SFMI):

This (3778) (houtos)

Will be (2071)

Blessed (3107) (makarios)

Does (4162) is more literally doing.

Spurgeon writes that...