In Adversus haereses 4.17.4 - 4.18.6 Irenaeus develops the Eucharist as the completion of the figurative sacrifices of the old covenant. He concludes this section with a reference to the heavenly temple: the Christian sacrifice of Eucharist and prayer is offered to God on the altar in heaven (Iren. Haer. 4.18.6). The meaning of this passage in Irenaeus has not received much scholarly attention. How does Irenaeus understand the relations between earth and heaven, between present reality and eschatological hopes, in the context of Eucharistic worship? This paper analyses how Irenaeus develops his theology on this point out of the struggle with Valentinianism. Despite the Valentinian interest for hyper-cosmic divine realms and ascent-mysticism, Irenaeus does not refrain from using imagery of elevation, ascension, and participation in heavenly realities in his own account of the Christian faith. The different Valentinian systems all assumed salvation in terms of a separation of the spiritual from the material, heavenly from earthly. Irenaeus takes the Eucharist as a sign of the opposite. In and through the body of Christ the earth and material creation are not separated from, but rather united with heaven and the divine. In the Eucharistic celebration worshippers enter heaven as they offer the Eucharist, the "first-fruits of creation," at the heavenly altar. Through Christ as mediator they stand in the presence of the Father. From God they receive creation sanctified, the "first-fruits of God's gifts." In the Eucharist the eschatological union between humanity and God, between earth and heaven, is anticipated.