John 13:1-17, 31-35
"I give you a new commandment, that you love one another. Just as I have loved you, you also should love one another. By this everyone will know that you are my disciples, if you have love for one another."
Many Christians refer to the Thursday of Holy Week as "Maundy Thursday." The word 'Maundy' is an old one, and with all old words, there is some question about where it comes from. But, it's generally taken to be some variation of the word we know today as 'mandate.' Mandate means 'command,' so Maundy Thursday, which remembers the Last Supper, specifically remembers that command that Jesus gave at that supper: Love one another.
The text calls this is "new" command, but it's not new in the sense of being different from the scriptures that Jesus has been teaching all along. Jesus is essentially quoting the Old Testament summary of the law (if you're curious, check out Leviticus 19:18 where, in the middle of many hard to understand rules, there is an almost identical message about love).
Jesus, then, in the last days of his life when he had his disciples' attention most fully, chose to tell them to focus on love. And so today, on Maundy Thursday, we remember that all Communion celebrations at church, are meant to steer us back onto the path of love. Let us love one another as Christ has loved us.