"To swear by him whom I profess to love,
That I will work against him."
I read to for 'by,' in which I had been anticipated by Johnson, who was followed by Malone. 'Swear' naturally suggested 'by' to the printer's mind. (See on Macb. i. 5, R. and J. i. 1.)
"For what's more monstrous, more a prodigy,
Than to hear me protest truth of affection
Unto a person that I would dishonour?"
Jonson, New Inn, iii. 2.
The same sentiment is expressed in "Yes, as I love the woman that wrong'd him" (Meas. for Meas. ii. 3). In this speech of Diana's, Mr. Staunton would give 'Then pray you ... love you ill' to Bertram; but without any great advantage.