Proverbs 16:31

Note, 1. It ought to be the great care of old people to be found in the way of righteousness, the way of religion and serious godliness. Both God and man will look for them in that way; it will be expected that those that are old should be good, that the multitude of their years should teach them the best wisdom; let them therefore be found in that way. Death will come; the Judge is coming; the Lord is at hand. That they may be found of him in peace, let them be found in the way of righteousness (Pe2 3:14), found so doing, Mat 24:46. Let old people be old disciples; let them persevere to the end in the way of righteousness, which they long since set out in, that they may then be found in it. 2. If old people be found in the way of righteousness, their age will be their honour. Old age, as such, is honourable, and commands respect (Thou shalt rise up before the hoary head, Lev 19:32); but, if it be found in the way of wickedness, its honour is forfeited, its crown profaned and laid in the dust, Isa 65:20. Old people therefore, if they would preserve their honour, must still hold fast their integrity, and then their gray hairs are indeed a crown to them; they are worthy of double honour. Grace is the glory of old age.

— Matthew Henry's Concise Commentary (public domain)

(Compare Pro 20:29). if--or, which may be supplied properly, or without it the sense is as in Pro 3:16; Pro 4:10, that piety is blessed with long life.

— Jamieson-Fausset-Brown Commentary (public domain)