Adam Clarke on Hebrews 12:14

Follow peace with all men - Cultivate, as far as you possibly can, a good understanding, both with Jews and Gentiles. Ειρηνην διωκετε, pursue peace with the same care, attention, and diligence, as beasts do their game; follow it through all places; trace it through all winding circumstances; and have it with all men, if you can with a safe conscience.

And holiness - Τον ἁγιασμον· That state of continual sanctification, that life of purity and detachment from the world and all its lusts, without which detachment and sanctity no man shall see the Lord - shall never enjoy his presence in the world of blessedness. To see God, in the Hebrew phrase, is to enjoy him; and without holiness of heart and life this is impossible. No soul can be fit for heaven that has not suitable dispositions for the place.