Quotations about:
    skill

Virtues, however, we acquire by first exercising them. The same is true with skills, since what we need to learn before doing, we learn by doing; for example, we become builders by building, and lyre-players by playing the lyre. So too we become just by doing just actions, temperate by temperate actions, and courageous by courageous actions.

[τὰς δ’ ἀρετὰς λαμβάνομεν ἐνεργήσαντες πρότερον, ὥσπερ καὶ ἐπὶ τῶν ἄλλων τεχνῶν· ἃ γὰρ δεῖ μαθόντας ποιεῖν, ταῦτα ποιοῦντες μανθάνομεν, οἷον οἰκοδομοῦντες οἰκοδόμοι γίνονται καὶ κιθαρίζοντες κιθαρισταί· οὕτω δὴ καὶ τὰ μὲν δίκαια πράττοντες δίκαιοι γινόμεθα, τὰ δὲ σώφρονα σώφρονες, τὰ δ’ ἀνδρεῖα ἀνδρεῖοι.]

Aristotle (384-322 BC) Greek philosopher

Nicomachean Ethics [Ἠθικὰ Νικομάχεια], Book 2, ch. 1 (2.1, 1103a.32ff) (c. 325 BC) [tr. Crisp (2000)]
    (Source)

(Source (Greek)). Alternate translations:

But the Virtues we get by first performing single acts of working, which, again, is the case of other things, as the arts for instance; for what we have to make when we have learned how, these we learn how to make by making: men come to be builders, for instance, by building; harp-players, by playing on the harp: exactly so, by doing just actions we come to be just; by doing the actions of self-mastery we come to be perfected in self-mastery; and by doing brave actions brave.
[tr. Chase (1847)]

But the virtues we acquire by previous practice of their acts, exactly as we acquire our knowledge of the various arts. For, in the case of the arts, that which we have to be taught to do, that we learn by doing it. We become masons, for instance, by building; and harpers b y playing upon the harp. And so, in like manner, we become just by doing what is just, temperate by doing what is temperate, and brave by doing what is brave.
[tr. Williams (1869), sec. 23]

But the virtues we acquire by first exercising them, as is the case with all the arts, for it is by doing what we ought to do when we have learnt the arts that we learn the arts themselves; we become e.g. builders by building and harpists by playing the harp. Similarly it is by doing just acts that we become just, by doing temperate acts that we become temperate, by doing courageous acts that we become courageous.
[tr. Welldon (1892)]

But the virtues we acquire by doing the acts, as is the case with the arts too. We learn an art by doing that which we wish to do when we have learned it; we become builders by building, and harpers by harping. And so by doing just acts we become just, and by doing acts of temperance and courage we become temperate and courageous.
[tr. Peters (1893)]

But the virtues we get by first exercising them, as also happens in the case of the arts as well. For the things we have to learn before we can do them, we learn by doing them, e.g. men become builders by building and lyreplayers by playing the lyre; so too we become just by doing just acts, temperate by doing temperate acts, brave by doing brave acts.
[tr. Ross (1908)]

The virtues on the other hand we acquire by first having actually practised them, just as we do the arts. We learn an art or craft by doing the things that we shall have to do when we have learnt it: for instance, men become builders by building houses, harpers by playing on the harp. Similarly we become just by doing just acts, temperate by doing temperate acts, brave by doing brave acts.
[tr. Rackham (1934), ch. 1, sec. 4]

The virtues, by contrast, we acquire by first engaging in the activities, as is also true in the case of the various crafts. For the things we cannot produce without learning to do so are the very ones we learn to produce by producing them -- for example, we become builders by building houses and lyre players by playing the lyre. Similarly, then, we become just people by doing just actions, temperate people by doing temperate actions, and courageous people by doing courageous ones.
[tr. Reeve (1948)]

In the case of the virtues, on the other hand, we acquire them as a result of prior activities; and this is like the case of the arts, for that which we are to perform by art after learning, we first learn by performing, e.g., we become builders by building and lyre-players by playing the lyre. Similarly, we become just by doing what is just, temperate by doing what is temperate, and brave by doing brave deeds.
[tr. Apostle (1975)]

Virtues, by contrast, we acquire, just as we acquire crafts, by having previously activated them. For we learn a craft by producing the same product that we must produce when we have learned it, becoming builders, for instance, by building and harpists by playing the harp, so also, then, we become just by doing just actions, temperate by doing temperate actions, brave by doing brave actions.
[tr. Irwin/Fine (1995)]

For as regards those things we must learn how to do, we learn by doing them -- for example by building houses, people become house builders, and by playing the cithara, they become cithara players. So too, then, by doing just things become just; moderate things, moderate; and courageous things, courageous.
[tr. Bartlett/Collins (2011)]

We develop virtues after we have practiced them beforehand, the same way it works with the other arts. For, we learn as we do those very things we need to do once we have learned the art completely. So, for example, men become carpenters by building homes and lyre-players by practicing the lyre. In the same way, we become just by doing just things, prudent by practicing wisdom, and brave by committing brave deeds.
[tr. @sentantiq (2017)]