"Grant me help O Lord, from trouble, for vain is the salvation of man.
How often have I failed to find faith there where I thought I might depend upon it - and how often have I found it where I did not expect it?
Vain, therefore, is all hope in men; but the safety of the just is in you, O Lord.
Whom shall I believe O Lord but you? You are the truth who cannot deceive nor be deceived.
On the other hand, every man is a liar - infirm, unstable, and subject to fail - especially in words; so we shouldn't be so quick in believing even that which in appearance seems to sound right.
How wisely did you forewarn us to beware of men, and that a man's enemies are they of his own household, and that we are not to believe, if anyone should say, 'Behold here! or Behold there!'" - Imitation, Bk. III, Ch. 45
"It is better to leave everyone to his own way of thinking, than to give way to contentious discourses." Ibid, Ch. 44