“Men's consciences ought in no sort to be violated, urged, or constrained.”

Speech to the Electors of Bristol (3 November 1774); reported in The Works of the Right Honorable Edmund Burke (1899), vol. 2, p. 95
Context: Certainly, Gentlemen, it ought to be the happiness and glory of a representative to live in the strictest union, the closest correspondence, and the most unreserved communication with his constituents. Their wishes ought to have great weight with him; their opinions high respect; their business unremitted attention. It is his duty to sacrifice his repose, his pleasure, his satisfactions, to theirs,—and above all, ever, and in all cases, to prefer their interest to his own.
But his unbiased opinion, his mature judgment, his enlightened conscience, he ought not to sacrifice to you, to any man, or to any set of men living. These he does not derive from your pleasure,—no, nor from the law and the Constitution. They are a trust from Providence, for the abuse of which he is deeply answerable. Your representative owes you, not his industry only, but his judgment; and he betrays instead of serving you if he sacrifices it to your opinion.

1850s, Latter-Day Pamphlets (1850), The Present Time (February 1, 1850)
Context: Who would govern that can get along without governing? He that is fittest for it, is of all men the unwillingest unless constrained.

of HIV/AIDS
Address to the Pan Pacific HIV/AIDS Conference, Auckland, New Zealand, October 2005

"A Clean Conscience Never Relaxes"
I'm a Stranger Here Myself (1938)

1840s, Essays: First Series (1841), Prudence

Book IV, Part 2, Section 4
Religion within the Limits of Reason Alone (1793)
Context: The question here is not, “How conscience ought to be guided? For Conscience is its own General and Leader; it is therefore enough that each man have one. What we want to know is, how conscience can be her own Ariadne, and disentangle herself from the mazes even of the most raveled and complicated casuistical theology. Here is an ethical proposition that stands in need of no proof: No Action May At Any Time Be Hazarded On The Uncertainty That Perchance It May Not Be Wrong (Quod dubitas, ne feceris! Pliny - which you doubt, then neither do) Hence the Consciousness, that Any Action I am about to perform is Right, is in itself a most immediate and imperative duty. What actions are right, - what wrong – is a matter for the understanding, not for conscience. p. 251

Introductory
The Grammar of Science (1900)

The History of Freedom in Antiquity (1877)

As quoted in Divine Harmony: The Life and Teachings of Pythagoras by John Strohmeier and Peter Westbrook. (1999)
The Golden Verses
Context: Many words befall men, mean and noble alike; do not be astonished by them, nor allow yourself to be constrained.
If a lie is told, bear with it gently.
But whatever I tell you, let it be done completely.
Let no one persuade you by word or deed to do or say whatever is not best for you.