If So-and-so challenges me, I shall lay before you a careful account of what I have said and done; if he should continue, I shall reciprocate his dislike of me.
Tiberius, as quoted by Suetonius in De vita Caesarum, Chapter 28, in this form:
Exstat et sermo eius in senatu percivilis: ‘Siquidem locutus aliter fuerit, dabo operam ut rationem factorum meorum dictorumque reddam; si perseveraverit, in vicem eum odero.’
A remarkably modest statement of his is recorded in the Proceedings of the Senate: “If So-and-so challenges me, I shall lay before you a careful account of what I have said and done; if he should continue, I shall reciprocate his dislike of me.”