Tertullian, A. D. 200, is the next writer who uses the term Lord’s day. He defines his meaning, and fixes the name upon the day of Christ’s resurrection. Kitto[451] says this is “the earliest authentic instance” in which the name is thus applied, and we have proved this true by actual examination of every writer, unless the reader can discover some reference to Sunday in Clement’s mystical eighth day. Tertullian’s words are these:— “We, however (just as we have received), only on the Lord’s day of the resurrection [_solo die dominico resurrexionis_] ought to guard, not only against kneeling, but every posture and office of solicitude; deferring even our business, lest we give any place to the devil. Similarly, too, in the period of Pentecost; which period we distinguish by the same solemnity of exultation.”[452] Twice more does Tertullian use the term Lord’s day, and once more does he define it, this time calling it the “eighth day.” And in each of these two cases does he place the day which he calls Lord’s day in the same rank with the Catholic festival of Pentecost, even as he does in the instance already quoted. As the second instance of Tertullian’s use of Lord’s day, we quote a portion of the rebuke which he addressed to his brethren for mingling with the heathen in their festivals. He says:— “Oh! better fidelity of the nations to their own sects, which claims no solemnity of the Christians for itself! Not the Lord’s day, not Pentecost, _even if they had known them_, would they have shared with us; for they would fear lest they should seem to be Christians. _We_ are not apprehensive lest we seem to be _heathens_! If any indulgence is to be granted to the flesh, you have it. I will not say your own days, but more too; for to the _heathens_ each festive day occurs but once annually; _you_ have a festive day every eighth day.”[453] The festival which Tertullian here represents as coming every eighth day was no doubt the one which he has just called the Lord’s day. Though he elsewhere[454] speaks of the Sunday festival as observed at least by some portion of the heathen, he here speaks of the Lord’s day as unknown to those heathen of whom he now writes. This strongly indicates that the Sunday festival had but recently begun to be called by the name of Lord’s day. But he once more speaks of the Lord’s day:—