Depending on which church tradition you grew up in - you might think of today as Maundy Thursday. Regardless of which tradition you grew up in - it was on this night so long ago that Jesus celebrated the Last Supper with His disciples. This would be the supper depicted by DaVinci in that incredible masterpiece which shows the Apostle John seated right next to Jesus - the same Apostle who self-identified as "the disciple whom Jesus loved" (John 19:26, 21;7). This is the same Apostle John writing to us about love in this first of his three epistles.
And - this verse - maybe sums up John's experience as a Jesus' beloved disciple - turned Apostle - who outlived all his fellow disciples long enough to be exiled in his old age to the island of Patmos. John lived through an unbelievably wild slice of world history. Of all the things he could use pen and paper to record for us - this is what He has to say. John is an old man at this point - probably born around 10 years after Jesus was - in 6 a.d. Here is is around 95 a.d. - looking back over the better share of nine decades.
Perhaps - to John - this is his classic sermon, the way he told the gospel. When Jesus first called His disciples, He referred to John and his brother James as "sons of thunder" and while we don't know precisely what that means - one interpretation I grew up hearing was that John and his brother had a temper. Imagine - a young, hot-headed man, being so impressed with Jesus that after a long life of ministry and service - what he wants to tell us - is that Jesus loved us first.
Thank GOODNESS He did, too! We didn't have it in us to love Him - but that didn't stop Him from loving us - from introducing us to God's love, God's grace - and teaching us to love one another.