1 Peter 1.21 " Through him you have come to trust in God, who raised him from the dead and gave him glory, so that your faith and hope are set on God.
22 Now that you have purified your souls by your obedience to the truth so that you have genuine mutual love, love one another deeply from the heart.
23 You have been born anew, not of perishable but of imperishable seed, through the living and enduring word of God."
This is the wonderful thing we need to strive for, namely, a genuine mutual love whereby we love one another deeply from the heart.
This means that because we know the love of God and we know the truth that has changed us, we should have a genuine mutual love for others Christians and non-Christians.
This love by definition is "not simply an outward appearance or profession of love." It is part and parcel of the Christian life and not an optional extra. It’s a command from Christ.
The New English Bible translation has it "Love until you feel sincere affection towards your brother (or sister) Christians".
Love one another deeply from the heart is the icing on the cake here. This word love (agape) is a strong word meaning a "strong, deep affectionate love". Here Peter makes it doubly stronger "love (agape) one another deeply from the heart". This means extend the love to the point it is deeply felt, with "fervent earnest desire and emotion". It is love that loves despite feelings, but in the loving the feelings of love come. Love like this changes the world. Love like this will change our neighbourhood. Let us love like this.
Jesus said "By this everyone will know that you are my disciples, if you have love for one another."