Strive for peace with everyone, and for the holiness without which no one will see the Lord.
Hebrews 12:14 – Scripture of the Day (January 15, 2014)
Jesus said that the peacemakers will be blessed (Matt. 5:9). The Holy Spirit commanded us to be at peace with all if possible, so far as it depends on us (Rom. 12:18). Jesus implied that being peaceable was an indicator that you are the salt of the earth (Mark 9:50). The kingdom of God consists of peace along with righteousness and joy (Rom. 14:17). Christians are commanded to live in peace by aiming for restoration, comforting one another, and agreeing with one another (2 Cor. 13:11). Division and contentiousness are condemned (1 Cor. 1:10ff; Tit. 3:9-11).
In like manner, holiness (being different, set apart from the world) is essential for salvation. That sanctification comes only from the truth of God’s Word (John 17:17), which is holy itself and which will be rejected by those who are not peaceful (Matt. 7:6). Dedicating our entire lives to God is what makes us holy and acceptable to him (Rom. 12:1). He chose the church before the events of Genesis for one purpose: to be holy (Eph. 1:4), and that was also why he died on the cross (Col. 1:22).
To be at peace. To be holy, different from the world. That’s a big part of what true Christianity is all about.
Pre-Denominational Christianity 
The “everyone” of Heb. 12:14 would especially include those who were persecuting the Christians. Throughout Hebrews, there is encouragement to continue in the new covenant of Jesus (the great High Priest, who ministers not in an earthly “holy” sanctuary but in heaven). Thus Heb. 12:12-13 encourages them to strengthen their weak bodies (due to opposition from their former synagogues) and to follow Jesus, “the perfecter of our faith, who for the joy that was set before him endured the cross, despising the shame” (12:2). Just as Jesus was made “perfect through suffering,” so those joining him are also sanctified, becoming his “brothers” (and sisters) (Heb. 2:10-11). To become part of this holy family of God and His Son does set us apart for joy and glory in heaven; but on earth we also must endure suffering from those who find holiness elsewhere (like in the synagogue). To remain holy we must not revert back to joining other “holy families” (such as returning to the synagogues); and we must not try to overcome enemies by overpowering them, but rather strive for peace even with them. For we follow the faithful Son, who “learned obedience through what he suffered; and being made perfect he became the source of salvation for all who obey him” (5:9).