Tertullian

“ If men have consecrated for themselves this custom from superstition, why do you, estranged as you are from all their vanity, participate in solemnities consecrated to idols; as if for you also there were some prescript about a day, short of the observance of a particular day, to prevent your paying or receiving what you owe a man, or what is owed you by a man? ”

“ But, for these purposes, “There is nought of communion between light and darkness,” [3] between life and death or else we rescind what is written, “The world shall rejoice, but ye shall grieve.” [4] If we rejoice with the world, there is reason to fear that with the world we shall grieve too. But when the world rejoices, let us grieve; and when the world afterward grieves, we shall rejoice. ”

“ For why should you skulk withal, when you contaminate your own conscience by your neighbour’s ignorance? If you are not unknown to be a Christian, you are tempted, and you act as if you were not a Christian against your neighbour’s conscience ”