"little children, abide in Him, that when He appears, we may have confidence and not be ashamed before Him at His coming" - 1 John 2:28
1 John is written in the very last part of the 1st century. 60+ or more years after Jesus started his ministry in 27 A.D. and the beginning of the New Covenant church that began in 31 A.D. on the Holy Day of Pentecost.
The Aged Apostle John, the last remaining original Apostle, was in his late 80s or even 90s when he wrote 1 John.
When the Apostle John writes 1 John is likely one the only ones alive who heard directly the teachings that Jesus brought from the Father, saw Jesus suffer and die, saw the resurrected Jesus, ate meals with him, and after 40 days saw Jesus rise up into the clouds.
The Apostle John contrasts
1 John is a most instructive book for us to study and review as a congregation.