having purified your souls in obedience to the truth to the extent a sincere brotherly love, agape love for one another fervently from a pure heart (1 Peter 1:22)
Pure love is a type of love that is unconditional, compassionate, and generous. God is pure and God is love. A sign of being like God is love. Not some causal acquaintance, it should be real or sincere within your church with a fervent love. A pure heart agape loves earnestly or fervent which conveys a since of wholeheartedness or intensity; without slack, strenuously, without undue let up. Love is a sign of a pure heart.
and to the extent all of these, agape love which exists that which binds together to maturity (Colossians 3:14)
Faith is energized and actionable through love, this is what strengthens the church (Galatians 5:6). Above all the other virtues the greatest is love. "Having put on the new man, that renewed in knowledge according to its creator, as elect of God we should have heartfelt compassion, kindness, humility, gentleness, and long suffering..." (Colossians 3:12-14). But above all these is love.
For you were called to freedom, brothers. Only do not use your freedom as an opportunity for the flesh, but through love serve one another (Galatians 5:13)
We must first have a strong foundation before we have strength to grasp the love of Christ that is without bounds, and knits us together so nothing can separate us from his love. Then we can be filled to the fullness of God, becoming mature. We will be known as his disciples by our love for one another. Taught and disciplined in truth, sincerely loved, we purified our souls and from that pure heart comes fervent love for one another.