Maundy Thursday

 mandatum novum do vobis ut diligatis invicem sicut dilexi vos ut et vos diligatis invicem in hoc cognoscent omnes quia mei discipuli estis si dilectionem habueritis ad invicem (Vulgate)

A new commandment I give unto you, That ye love one another; as I have loved you, that ye also love one another. (KJV) 

John 13:34-35

On the night of the last supper, Jesus told his disciples that he gave to them a new commandment.  From the Latin "mandatum," to command, comes the name attached to the Thursday of Holy Week.  Maundy Thursday is the night upon which we commemorate the Last Supper and the betrayal of Jesus' by Judas Iscariot.