How can you say that the sacraments are anything more than symbolic acts?
Many modern-day Protestants wonder if sacraments are not merely the outward expression of an inward faith or activity. Obviously the Orthodox Church would answer that the sacraments--or mysteries--are much more than that. But before looking at the evidence for that being true of specific sacraments, it might be better to start out with something more basic: that God uses the world--in all it’s glorious materiality--to bring about His will.
In the Gospel of Mark, for example, Jesus used spit to help heal blindness (Mk. 8:22-26). And in the Gospel of John it is spit, dirt and water which are all used: “When [Jesus] had thus spoken, he spat on the ground, and made clay of the spittle, and he anointed the eyes of the blind man with the clay, And said unto him, Go, wash in the pool of Siloam, (which is by interpretation, Sent.) He went his way therefore, and washed, and came seeing. “ (Jn. 9:6-7) So to was there a woman who was sick for twelve years who was healed not just by faith, but by putting that faith into action. It was not just by having faith that God healed her, but when she “came behind [Jesus], and touched the order of his garment” (Lk. 8:43-44) And it was said that, through the work of an angel of God, the water in the pool of Bethesda in Jerusalem sometimes had healing powers (Jn. 5:2-4)
Other Scriptural examples of God working through the material world would include Paul’s handkerchiefs healing people of bodily and demonic illnesses (Acts 19:11-12), and when the bones of Elisha resurrected a man (2 Kings 13:20-21)
Humanity itself, also, can be included in this. For while people have a soul and spirit, they also have a body, and use that body to help them think, communicate and act. Thus when God saves people through the prayers, preaching, teaching, etc. of people (cf 1 Tim. 4:16; James 5:19-20; Rom. 11:13-14; etc.), this work is facilitated, to at least some extent, through the use of plain old matter.
Thus God does not just focus on some nebulous, abstract “faith,” but makes use of other aspects of his creation to bring about His will, including things that are concrete and common, or even quite coarse. Now, as for the actual sacraments mentioned in Scripture, the two most prominent ones are baptism and the eucharist.
For various reasons, God chose the practice of baptism as a way of incorporating people in the body body of Christ (1 Cor. 12:13). Thus Scripture clearly teaches that Jesus commanded the Church to baptize (Matt. 28:19), and the book of Acts repeatedly mentions the early Church baptizing people who wished to convert (Acts 2:38-41; 8:5-12; 10:48; 18:7-8; 22:16; etc.). Baptism was more than just a sign of conversion, however, but also according to Scripture has a part to play in the life in Christ (Rom. 6:3-4; Gal. 3:27), and even ultimately has a part to play in the salvation of most Christians (Mk. 16:16; Jn. 3:5; 1 Pet. 3:17-22).
The eucharist is also an act that has importance in itself, not merely as an activity participated in because of faith, but as a grace-bestowing thing in itself. For the Orthodox, the Gospel passages mentioning the last supper (Mt. 26:20-29; Mk. 14:17-31; Lk. 22:14-31) seem clear: “this is my body” and “this is my blood” are to be taken literally, though admittedly how it becomes the body and blood is a mystery. Thus our Lord, speaking of the eucharist to come afterwards, said: “Verily, verily, I say unto you, Except ye eat the flesh of the Son of man, and drink his blood, ye have no life in you” (Jn. 6:53). This offended many of his followers, who left him because of this idea (Jn. 6:59-66). Jesus didn’t go running after them, however, saying “No! I was speaking metaphorically!” Jesus knew that the concept would be off-putting, especially to Jews, but he didn‘t back down, or soften his words.
The other prominent passages dealing with the eucharist are found in the First Epistle to the Corinthians. It is true that in this work St. Paul says that communion serves as a rememberance and proclamation of the death of Jesus (1 Cor. 11:23-26). This purpose of this sacrament is more than that, though, for through a mystery it unites the body of Christ (1 Cor. 10:16-17; Eph. 5:30), and to partake of the eucharist frivolously was a very serious offense (1 Cor. 11:27-30). St. Paul even went so far as to say that: “he that eateth and drinketh unworthily, eateth and drinketh damnation to himself, not discerning the Lord's body” (1 Cor. 11:29)
We find similar words about the importance and grace of the sacraments in the early Christian writings. St. Ignatius of Antioch (d. c. 107 CE), for example, called the eucharist the "medicine of immortality" (Epistle to the Ephesians, 20; cf Epistle to the Romans, 7), and says of heretics: "They abstain from the Eucharist and from prayer, because they confess not the Eucharist to be the flesh of our Saviour Jesus Christ, which suffered for our sins, and which the Father, of His goodness, raised up again. Those, therefore, who speak against this gift of God, incur death in the midst of their disputes." (Epistle to the Smyrnaeans, 7)
St. Justin Martyr (d. c. 165 CE) also spoke explicitly of the eucharist:
And this food is called among us Εὐχαριστία [the Eucharist], of which no one is allowed to partake but the man who believes that the things which we teach are true, and who has been washed with the washing that is for the remission of sins, and unto regeneration, and who is so living as Christ has enjoined. For not as common bread and common drink do we receive these; but in like manner as Jesus Christ our Saviour, having been made flesh by the Word of God, had both flesh and blood for our salvation, so likewise have we been taught that the food which is blessed by the prayer of His word, and from which our blood and flesh by transmutation are nourished, is the flesh and blood of that Jesus who was made flesh.
-- St. Justin Martyr, First Apology, 66
And there was also St. Irenaeus (d. 202 CE), who said:
But vain in every respect are they who despise the entire dispensation of God, and disallow the salvation of the flesh, and treat with contempt its regeneration, maintaining that it is not capable of incorruption. But if this indeed do not attain salvation, then neither did the Lord redeem us with His blood, nor is the cup of the Eucharist the communion of His blood, nor the bread which we break the communion of His body...
When, therefore, the mingled cup and the manufactured bread receives the Word of God, and the Eucharist of the blood and the body of Christ is made, from which things the substance of our flesh is increased and supported, how can they affirm that the flesh is incapable of receiving the gift of God, which is life eternal, which [flesh] is nourished from the body and blood of the Lord, and is a member of Him?— even as the blessed Paul declares in his Epistle to the Ephesians, that “we are members of His body, of His flesh, and of His bones.” (Eph. 5:30)
-- St. Irenaeus, Against Heresies, 5, 2, 2-3