The following is from thewestminsterstandard.org:
A. The Lord’s Supper is a Sacrament, wherein, by giving and receiving bread and wine, according to Christ’s appointment, his death is showed forth; and the worthy receivers are, not after a corporal and carnal manner, but by faith, made partakers of his body and blood, with all his benefits, to their spiritual nourishment and growth in grace.
Q. 97. What is required to the worthy receiving of the Lord’s Supper?
A. It is required of them that would worthily partake of the Lord’s Supper, that they examine themselves, of their knowledge to discern the Lord’s body, of their faith to feed upon him, of their repentance, love, and new obedience; lest, coming unworthily, they eat and drink judgment to themselves.
Q. 98. What is prayer?
A. Prayer is an offering up of our desires unto God, for things agreeable to his will, in the name of Christ, with confession of our sins, and thankful acknowledgment of his mercies.
Q. 99. What rule hath God given for our direction in prayer?
A. The whole Word of God is of use to direct us in prayer, but the special rule of direction is that form of prayer which Christ taught his disciples, commonly called, The Lord’s Prayer.
Q. 100. What doth the preface of the Lord’s Prayer teach us?
A. The preface of the Lord’s Prayer, which is, Our Father which art in heaven,” teacheth us to draw near to God with all holy reverence and confidence, as children to a father, able and ready to help us; and that we should pray with and for others.
Recommended sermon: The Westminster Assembly, by Dr. Sinclair B. Ferguson
