John Trapp on Proverbs 20:29

Verſ. 29. The glory of young men is their ſtrength] ſc. If well uſed, in following their Callings, and fighting for their Countries, as thoſe young men of the Princes of the Provinces did, 1 King. 20.20. and not in quarrelling and Duelling, as thoſe yongſters of Helketh-hezzurim, 2 Sam. 2. who ſheathed their ſwords in their fellows bowels.

And the beauty of old men is their gray-head] That ſilver crown of hoary hairs (ſaith one) which the finger of God doth ſet upon their heads, makes them Venerable in all places where they come: ſo that they carry an authority or majeſty with them, as it were. See the Note on chap. 16.31.