Let me state why I, with John Calvin, oppose paedocommunion. But first, to note age thesholds, it would be helpful if the reader would study the following passages preferably in the original Hebrew or Greek: Gen. 2:17-24; 14:13-24; 17:23-27; 22:2-19; Ex. 12:3-4, 8-11, 26-27,37, 43-48; Num. 9:2-13; Prov. 22:6; Lam. 2:12; 4:4; Luke 2:40-52; 22:1-20; John 6:2-4,10,53; Acts 22:3; I Cor. 5:7-13f; 10:1-22; 11:1-10,20-34; 13:11; 14:20-37; Phil. 3:5; I Tim. 2:8-15; 6:12f; Heb. 5:12 to 6:2; I John 2:12f; and Rev. 2:20f.
I oppose all attempts to reconstruct the clearly antipaedocommunionistic teaching of our Westminster Confession 28:1 & 29:3,8 & 31:4 and our Westminster Larger Catechism QQ. 169-177. True Presbyterians and other men of like persuasion respect Calvin's views in his Commentaries on Ex. 12:24-43; Lam. 2:12; John 6:53 & Heb. 6:2; in his Sermons on Deuteronomy 16:1-8 cf. vv. 16f; and his Institutes IV:13:6 & IV:16:30 & IV:19:4f.
1, infant baptism signifies regeneration (but not conversion);
2, one's first communion at teenage signifies conversion (not regeneration);
3, Eucharist replaces the Passover (but not circumcision);
4, the 1st-century B.C. Hebrew Essenes (and even the Pharisees), like the Karaites till today, restricted their Passovers to their (post-)adolescent males after prior catechization terminating in their Bar Mitzvah not before age 13 (cf. Prov. 22:6's chanoch with Luke 2:40-47 and 22:1-20);
5, no females nor any preteenagers ever partook of the Passover till it was thus deformed by Post-Christian Liberal Judaism (+/- 200 A.D.);
6, there is absolutely no trace whatsoever of paedocommunionism in patristic writings but only in pagan sources prior to 250 A.D.;
7, novel paedocommunionism is a ritualistic heterodoxy of the "Eastern Orthodox" and kindred denominations quite opposed to truly-orthodox Reformed Theology;
8, the practice of paedocommunionism abolishes the need first of catechization and then of profession of one’s faith before one’s own very first manducation at the sacrament;
9, paedocommunism ultimately leads to an uncatechized Church (which Calvin says cannot long continue without catechizing); and
10, Calvin in his Institutes (IV:16:30) accordingly concludes against the Anabaptists: “They object that there is not greater reason for admitting infants to Baptism than to the Lord’s Supper – to which, however, there are never admitted…. The Supper is intended for those of riper years, who, having passed…infancy, are fit to bear solid food…. They cannot partake worthily without being able duly to discern the sanctity of the Lord’s body. Why should we stretch out poison instead of vivifying food to our young children? … Circumcision, which as is well known corresponds to our Baptism, was intended for infants. But the Passover for which the Supper is substituted…was duly eaten only by those who were of an age sufficient to ask the meaning of it (Exod. 12:26). Had these men the least particle of soundness in their brain, would they thus be blind as to a matter so very clear and obvious?”