Traditions of the Eucharist were handed down in secondary writings

Those who have become acquainted with the secondary (i.e., under Christ) constitutions of the apostles, are aware that the Lord instituted a new oblation in the new covenant, according to [the declaration of] Malachi the prophet.

…For we make an oblation to God of the bread and the cup of blessing, giving Him thanks in that He has commanded the earth to bring forth these fruits for our nourishment. And then, when we have perfected the oblation, we invoke the Holy Spirit, that He may exhibit this sacrifice, both the bread the body of Christ, and the cup the blood of Christ, in order that the receivers of these antitypes may obtain remission of sins and life eternal.

Irenaeus of Lyons
Lost Writings
Fragment XXXVII

The Gospel of Matthew was written to the Jews

The Gospel according to Matthew was written to the Jews. For they laid particular stress upon the fact that Christ [should be] of the seed of David. Matthew also, who had a still greater desire [to establish this point], took particular pains to afford them convincing proof that Christ is of the seed of David; and therefore he commences with [an account of] His genealogy.

Irenaeus of Lyons
Lost Writings
Fragment XXIX

Christ’s body as the Ark of the Covenant

For as the ark [of the covenant] was gilded within and without with pure gold, so was also the body of Christ pure and resplendent; for it was adorned within by the Word, and shielded without by the Spirit, in order that from both [materials] the splendor of the natures might be clearly shown forth.

…so is that ark declared a type of the body of Christ, which is both pure and immaculate.

Irenaeus of Lyons
Lost Writings
Fragment VIII and XLVIII

The logos is a property of the soul endowed by God

The will and the energy of God is the effective and foreseeing cause of every time and place and age, and of every nature. The will is the reason (λόγος) of the intellectual soul, which [reason] is within us, inasmuch as it is the faculty belonging to it which is endowed with freedom of action.

Irenaeus of Lyons
Lost Writings
Fragment V

Differences in fasting customs between East and West are accepted

Thus, in fact, the difference [in observing] the fast establishes the harmony of [our common] faith. For neither could Anicetus persuade Polycarp to forego the observance [in his own way], inasmuch as these things had been always [so] observed by John the disciple of our Lord, and by other apostles with whom he had been conversant; nor, on the other hand, could Polycarp succeed in persuading Anicetus to keep [the observance in his way], for he maintained that he was bound to adhere to the usage of the presbyters who preceded him.

…so that they parted in peace one from the other, maintaining peace with the whole Church, both those who did observe [this custom] and those who did not.

Irenaeus of Lyons
Lost Writings
Fragment III

Irenaeus learned from Polycarp as a boy

For, while I was yet a boy, I saw thee in Lower Asia with Polycarp, distinguishing thyself in the royal court, and endeavouring to gain his approbation. For I have a more vivid recollection of what occurred at that time than of recent events (inasmuch as the experiences of childhood, keeping pace with the growth of the soul, become incorporated with it); so that I can even describe the place where the blessed Polycarp used to sit and discourse— his going out, too, and his coming in—his general mode of life and personal appearance, together with the discourses which he delivered to the people; also how he would speak of his familiar intercourse with John, and with the rest of those who had seen the Lord; and how he would call their words to remembrance. Whatsoever things he had heard from them respecting the Lord, both with regard to His miracles and His teaching, Polycarp having thus received [information] from the eye-witnesses of the Word of life, would recount them all in harmony with the Scriptures. These things, through, God’s mercy which was upon me, I then listened to attentively, and treasured them up not on paper, but in my heart; and I am continually, by God’s grace, revolving these things accurately in my mind.

Irenaeus of Lyons
Lost Writings
Fragment II

 

Man will become higher than the angels

For there is the one Son, who accomplished His Father’s will; and one human race also in which the mysteries of God are wrought, “which the angels desire to look into;” and they are not able to search out the wisdom of God, by means of which His handiwork, confirmed and incorporated with His Son, is brought to perfection; that His offspring, the First-begotten Word, should descend to the creature, that is, to what had been moulded (plasma), and that it should be contained by Him; and, on the other hand, the creature should contain the Word, and ascend to Him, passing beyond the angels, and be made after the image and likeness of God.

Irenaeus of Lyons
Against Heresies, Book V
Chapter XXXVI

The new flesh of the resurrection is the same as the old flesh

He promised to drink of the fruit of the vine with His disciples, thus indicating both these points: the inheritance of the earth in which the new fruit of the vine is drunk, and the resurrection of His disciples in the flesh. For the new flesh which rises again is the same which also received the new cup.

Irenaeus of Lyons
Against Heresies, Book V
Chapter XXXIII