The First Sunday after Easter
ALMIGHTY Father, who hast given thine only Son to die for our sins, and to rise again for our justification; Grant us so to put away the leaven of malice and wickedness, that we may always serve thee in pureness of living and truth; through the merits of the same thy Son Jesus Christ our Lord. Amen.
Source of Collect: Archbishop Cranmer [1549 AD]. This was originally used for the second communion, if any, on Easter. Lost in the 1552 revision, and restored in 1662. From 1 Cor v. 8 "Therefore let us keep the feast, not with old leaven, neither with the leaven of malice and wickedness; but with the unleavened bread of sincerity and truth." [Barbee and Zahl]
1 St. John v. 4.; Psalms 110, 111 | 2, 57; John xx. 19
Homily of Tertullian
Peace be unto you: as my Father hath sent me, even so send I you.
Psalm 110, 111 | 2, 57
1 St. John v. 4.
WHATSOEVER is born of God overcometh the world: and this is the victory that overcometh the world, even our faith. Who is he that overcometh the world, but he that believeth that Jesus is the Son of God? This is he that came by water and blood, even Jesus Christ; not by water only, but by water and blood. And it is the Spirit that beareth witness, because the Spirit is truth. For there are three that bear record [in heaven, the Father, the Son, and the Holy Ghost; and these three are one. And there are three that bear witness in earth, ] the Spirit, and the water, and the blood: and these three agree in one. If we receive the witness of men, the witness of God is greater: for this is the witness of God which he hath testified of his Son. He that believeth on the Son of God hath the witness in himself: he that believeth not God hath made him a liar; because he believeth not the record that God gave of his Son. And this is the record, that God hath given to us eternal life, and this life is in his Son. He that hath the Son hath life; and he that hath not the Son of God hath not life.Johannine Comma
St. John xx. 19.
THE same day at evening, being the first day of the week, when the doors were shut where the disciples were assembled for fear of the Jews, came Jesus and stood in the midst, and saith unto them, Peace be unto you. And when he had so said, he shewed unto them his hands and his side. Then were the disciples glad when they saw the Lord. Then said Jesus to them again, Peace be unto you: as my Father hath sent me, even so send I you. And when he had said this, he breathed on them, and saith unto them, Receive ye the Holy Ghost: whosesoever sins ye remit, they are remitted unto them; and whosesoever sins ye retain, they are retained.
Chapter xxv. Against Praxeas
Chapter XXV. The Paraclete, or Holy Ghost. He is Distinct from the Father and the Son as to Their Personal Existence. One and Inseparable from Them as to Their Divine Nature. Other Quotations Out of St. John's Gospel.
What follows Philip's question, and the Lord's whole treatment of it, to the end of John's Gospel, continues to furnish us with statements of the same kind, distinguishing the Father and the Son, with the properties of each. Then there is the Paraclete or Comforter, also, which He promises to pray for to the Father, and to send from heaven after He had ascended to the Father. He is called "another Comforter," indeed;  but in what way He is another we have already shown,  "He shall receive of mine," says Christ,  just as Christ Himself received of the Father's. Thus the connection of the Father in the Son, and of the Son in the Paraclete, produces three coherent Persons, who are yet distinct One from Another. These Three are, one  essence, not one Person,  as it is said, "I and my Father are One,"  in respect of unity of substance not singularity of number. Run through the whole Gospel, and you will find that He whom you believe to be the Father (described as acting for the Father, although you, for your part, forsooth, suppose that "the Father, being the husbandman,"  must surely have been on earth) is once more recognised by the Son as in heaven, when, "lifting up His eyes thereto,"  He commended His disciples to the safe-keeping of the Father.  We have, moreover, in that other Gospel a clear revelation, i.e. of the Son's distinction from the Father, "My God, why hast Thou forsaken me? "  and again, (in the third Gospel, ) "Father, into Thy hands I commend my spirit."  But even if (we had not these passages, we meet with satisfactory evidence) after His resurrection and glorious victory over death. Now that all the restraint of His humiliation is taken away, He might, if possible, have shown Himself as the Father to so faithful a woman (as Mary Magdalene) when she approached to touch Him, out of love, not from curiosity, nor with Thomas' incredulity. But not so; Jesus saith unto her, "Touch me not, for I am not yet ascended to my Father; but go to my brethren" (and even in this He proves Himself to be the Son; for if He had been the Father, He would have called them His children, (instead of His brethren), "and say unto them, I ascend unto my Father and your Father, and to my God and your God."  Now, does this mean, I ascend as the Father to the Father, and as God to God? Or as the Son to the Father, and as the Word to God? Wherefore also does this Gospel, at its very termination, intimate that these things were ever written, if it be not, to use its own words, "that ye might believe that Jesus Christ is the Son of God? "  Whenever, therefore, you take any of the statements of this Gospel, and apply them to demonstrate the identity of the Father and the Son, supposing that they serve your views therein, you are contending against the definite purpose of the Gospel. For these things certainly are not written that you may believe that Jesus Christ is the Father, but the Son. 
Let us reflect on Tertullian "On Prayer"
We are the true worshippers and the true priests: praying in spirit, we make our sacrifice of prayer in spirit, an offering which is God's own and acceptable to him. This is the offering which he has asked for, and which he has provided for himself. This is the sacrifice, offered from the heart, fed on faith, prepared by truth; unblemished in innocence, pure in chastity, garlanded with love, which we must bring to God's altar, in a procession of good works, to the accompaniment of psalms and hymns. It will obtain for us from God all that we ask. Amen
 John xiv. 16.  See above ch. xiii.  John xvi. 14.  Unum. [On this famous passage see Elucidation III.]  Unus.  John x. 30.  John xv. 1.  John xvii. 1.  John xvii. 11.  Matt. xxvii. 46.  Luke xxiii. 46.  John xx. 17.  John xx. 31.  [A curious anecdote is given by Carlyle in his Life of Frederick (Book xx. cap. 6), touching the text of "the Three Witnesses." Gottsched satisfied the king that it was not in the Vienna ms. save in an interpolation of the margin "in Melanchthon's hand." Luther's Version lacks this text.]