By these words at the Last Supper Jesus showed that, when his Body was nailed to the Cross and his Blood was poured out, he would be giving his life for us, so that we, instead of being separated from God by our sins, might be made at one with him.

So, when the Apostles had their next fellowship meal after the Crucifixion, they did as Jesus had commanded them and used the same words which he had first used at the Last Supper. It was in this way, and in this way alone, that they came to know and understand what Our Lord’s death had really meant, and so the fellowship meal became their chief service every Sunday at which they re-called before God the Crucifixion and thanked him for all Our Lord had done in saving us from the power of sin and uniting us to God. That is why this great Christian act of worship was called the Eucharist or Thanksgiving.