Tertullian argues that no one is worthy of heaven on the basis of merit

And yet the latter opinion ought to be discussed, that God conferred divine honours in consideration of meritorious claims. Well, then, if the award was made on such grounds, if heaven was opened to men of the primitive age because of their deserts, we must reflect that after that time no one was worthy of such honour; except it be, that there is now no longer such a place for any one to attain to.

Tertullian
Ad Nationes, Book II
Chapter XIII

Our souls will return to the same bodies

Ridicule, therefore, as much as you like the excessive stupidity of such minds as die that they may live; but then, in order that you may be able to laugh more merrily, and deride us with greater boldness, you must take your sponge, or perhaps your tongue, and wipe away those records of yours every now and then cropping out, which assert in not dissimilar terms that souls will return to bodies. But how much more worthy of acceptance is our belief which maintains that they will return to the same bodies!

Tertullian
Ad Nationes, Book I
Chapter XIX

The 2nd century Church prayed toward the east and worshipped on Sunday

Others, with greater regard to good manners, it must be confessed, suppose that the sun is the god of the Christians, because it is a well-known fact that we pray towards the east, or because we make Sunday a day of festivity.

Tertullian
Ad Nationes, Book I
Chapter XIII

Tertullian describes the cross as having a cross-beam as well as a stake

Every piece of timber which is fixed in the ground in an erect position is a part of a cross, and indeed the greater portion of its mass.  But an entire cross is attributed to us, with its transverse beam, of course, and its projecting seat.

…Since the head rises upwards, and the back takes a straight direction, and the shoulders project laterally, if you simply place a man with his arms and hands outstretched, you will make the general outline of a cross.

Tertullian
Ad Nationes, Book I
Chapter XII

The early Church held closed communion and the Romans spied on them and spread rumors

But why need I disparagingly refer to strange spies and informers, when you allege against us such charges as we certainly do not ourselves divulge with very much noise—either as soon as you hear of them, if we previously show them to you, or after you have yourselves discovered them, if they are for the time concealed from you? For no doubt, when any desire initiation in the mysteries, their custom is first to go to the master or father of the sacred rites.  Then he will say (to the applicant), You must bring an infant, as a guarantee for our rites, to be sacrificed, as well as some bread to be broken and dipped in his blood; you also want candles, and dogs tied together to upset them, and bits of meat to rouse the dogs.  Moreover, a mother too, or a sister, is necessary for you. What, however, is to be said if you have neither? I suppose in that case you could not be a genuine Christian. Now, do let me ask you, Will such things, when reported by strangers, bear to be spread about (as charges against us)? It is impossible for such persons to understand proceedings in which they take no part. The first step of the process is perpetrated with artifice; our feasts and our marriages are invented and detailed by ignorant persons, who had never before heard about Christian mysteries. And though they afterwards cannot help acquiring some knowledge of them, it is even then as having to be administered by others whom they bring on the scene. Besides, how absurd is it that the profane know mysteries which the priest knows not!  They keep them all to themselves, then, and take them for granted; and so these tragedies, (worse than those) of Thyestes or Œdipus, do not at all come forth to light, nor find their way to the public. Even more voracious bites take nothing away from the credit of such as are initiated, whether servants or masters. If, however, none of these allegations can be proved to be true, how incalculable must be esteemed the grandeur (of that religion) which is manifestly not overbalanced even by the burden of these vast atrocities! O ye heathen; who have and deserve our pity, behold, we set before you the promise which our sacred system offers. It guarantees eternal life to such as follow and observe it; on the other hand, it threatens with the eternal punishment of an unending fire those who are profane and hostile; while to both classes alike is preached a resurrection from the dead.

Tertullian
Ad Nationes, Book I
Chapter VII

The Lutherans saw their movement as not having introduced any innovations but only correcting abuses

Inasmuch, then, as our churches dissent in no article of the faith from the Church Catholic, but only omit some abuses which are new, and which have been erroneously accepted by the corruption of the times, contrary to the intent of the Canons, we pray that Your Imperial Majesty would graciously hear both what has been changed, and what were the reasons why the people were not compelled to observe those abuses against their conscience.

Augsburg Confession
Article XXI.X

Works cannot save a man

My most merciful and all-merciful God, O Lord Jesus Christ! In Thy great love, Thou didst come down and become flesh in order to save all. Again, I pray Thee, save me by Grace! If Thou shouldst save me because of my deeds, it would not be a gift, but merely a duty. Truly, Thou aboundest in graciousness and art inexpressibly merciful! Thou hast said, O my Christ: “He who believes in me shall live and never see death”. If faith in Thee saves the desperate, behold: I believe! Save me, for Thou art my God and my Maker. May my faith replace my deeds, O my God, for Thou wilt find no deeds to justify me. May my faith be sufficient for all. May it answer for me; may it justify me; may it make me a partaker of Thine eternal glory; and may Satan not seize me, O Word, and boast that He has torn me from Thy hand and fold. O Christ my Savior: save me whether I want it or not! Come quickly, hurry, for I perish! Thou art my God from my mother’s womb. Grant, O Lord, that I may now love Thee as once I loved sin, and that I may labor for Thee without laziness as once I labored for Satan the deceiver. Even more, I will labor for Thee, my Lord and God Jesus Christ, all the days of my life, now and ever and unto ages of ages. Amen.

Orthodox prayer for salvation by grace