He mentions his readers’ rebirth to give further grounds to the command to “love one another.” This cuts two ways:
God displayed immense love for them in bringing about their rebirth. As they have received much love, they are to display much love (John 13:34; John 15:12).
Since his readers have in fact been delivered from the womb of their former ignorance (1 Peter 1:14, when they did not know what love truly was), they now know how to love. So they need to follow through with a lifestyle that reflects what God has done in their lives.
23 since you have been born again, not of perishable seed but of imperishable, through the living and abiding word of God;