Souls continue to exist after death

For if He be not the God of the dead, but of the living, yet was called the God of the fathers who were sleeping, they do indubitably live to God, and have not passed out of existence, since they are children of the resurrection.

Irenaeus of Lyons
Against Heresies, Book IV
Chapter V

Paul and the saints pray for us

You are initiated into the mysteries of the Gospel with Paul, the holy, the martyred, inasmuch as he was “a chosen vessel;” at whose feet may I be found, and at the feet of the rest of the saints, when I shall attain to Jesus Christ, who is always mindful of you in His prayers.

Ignatius of Antioch
Epistle to the Ephesians
Chapter XII

Polycarp’s relics are preserved for use in the Church

Accordingly, we afterwards took up his bones, as being more precious than the most exquisite jewels, and more purified than gold, and deposited them in a fitting place, whither, being gathered together, as opportunity is allowed us, with joy and rejoicing, the Lord shall grant us to celebrate the anniversary of his martyrdom, both in memory of those who have already finished their course, and for the exercising and preparation of those yet to walk in their steps.

Martyrdom of Polycarp
Chapter XVIII

Christ is the only one worshipped

… It is neither possible for us ever to forsake Christ, who suffered for the salvation of such as shall be saved throughout the whole world (the blameless one for sinners), nor to worship any other. For Him indeed, as being the Son of God, we adore; but the martyrs, as disciples and followers of the Lord, we worthily love on account of their extraordinary affection towards their own King and Master, of whom may we also be made companions and fellow-disciples!

Martyrdom of Polycarp
Chapter XVII

Prayers to God and the Saints

Let us then also pray for those who have fallen into any sin, that meekness and humility may be given to them, so that they may submit, not unto us, but to the will of God. For in this way they shall secure a fruitful and perfect remembrance from us, with sympathy for them, both in our prayers to God and our mention of them to the saints.

Clement of Rome
First Epistle to the Corinthians
Chapter LVI