Ecclesia de Eucharistia §37

³⁷ The two sacraments of the Eucharist and Penance are very closely connected. Because the Eucharist makes present the redeeming sacrifice of the Cross, perpetuating it sacramentally, it naturally gives rise to a continuous need for conversion, for a personal response to the appeal made by Saint Paul to the Christians of Corinth: “We beseech you on behalf of Christ, be reconciled to God” ( 2 Cor 5:20). If a Christian's conscience is burdened by serious sin, then the path of penance through the sacrament of Reconciliation becomes necessary for full participation in the Eucharistic Sacrifice. The judgment of one's state of grace obviously belongs only to the person involved, since it is a question of examining one's conscience. However, in cases of outward conduct which is seriously, clearly and steadfastly contrary to the moral norm, the Church, in her pastoral concern for the good order of the community and out of respect for the sacrament, cannot fail to feel directly involved. The Code of Canon Law refers to this situation of a manifest lack of proper moral disposition when it states that those who “obstinately persist in manifest grave sin” are not to be admitted to Eucharistic communion.