You always heat this on mass or read it. The day before Christ was crucified, He commanded His disciples to continue observing the Lord's Supper or Communion. (Matthew 26:26-30)
1 Corinthians 11:23-29
"For I received from the Lord that which I also delivered to you: that the Lord Jesus on the same night in which He was betrayed took bread; and when He had given thanks, He broke it and said, 'Take, eat; this is My body which is broken for you; do this in remembrance of Me.' In the same manner, He also took the cup after supper, saying, 'This cup is the new covenant in My blood. This do, as often as you drink it, in remembrance of Me.' For as often as you eat this bread and drink this cup, you proclaim the Lord's death till He comes."Therefore whoever eats this bread or drinks this cup of the Lord in an unworthy manner will be guilty of the body and blood of the Lord. But let a man examine himself, and so let him eat of the bread and drink of the cup. For he who eats and drinks in an unworthy manner eats and drinks judgment to himself, not discerning the Lord's body."
The Lord's Supper is the remembrance of Jesus. It is a testimony. By partaking it, we testify that Jesus' body was broken for us and He shed his blood for us. Thereby, we proclaim His death. We are doing this in remembrance of Him. When we eat the bread and drink the cup of the wine, we remember His body and blood being sacrifices for the forgiveness of our sins. By testifying it, we also receive the grace of forgiveness.
1 Corinthians 10:16-17
"The cup of blessing which we bless, is it not the communion of the blood of Christ? The bread which we break, is it not the communion of the body of Christ? 17 For we, though many, are one bread and one body; for we all partake of that one bread."
