Among the moral self-restraints which an aspirant is required to practise is that of truthfulness. It is the second of Patanjali's five ethical injunctions for the would-be yogi. There are several reasons for this prescription. But the one which affects his quest directly is the effect of untruthfulness upon his inner being. It not only spoils his character and destiny but also deforms his mind. In the liar's mouth the very function of language becomes a perverted one. He renders defective the very instrument with which he is seeking to make his way to the Overself; it becomes spoiled. If he meets with any mystical experience, it will become mixed with falsity or hallucination. If he finds spiritual truth, it will not be the pure or whole truth but the distortion of it.
Where situations are likely to arise which make truth-telling highly undesirable, the earnest aspirant should try to avoid them as much as possible by forethought. The pattern of indifference to truth-speaking must be broken up. The pattern of scrupulous respect for truth must be built up. The discipline of his ego must include the discipline of its speech. His words must be brought into correspondence with his ideals. Every word written or uttered must be steel-die true. If the truth is awkward or dangerous to say, then it may be advisable to keep silent. May he tell a small white lie to liberate himself from an awkward situation? The answer is still the same: "Thou shalt not bear false witness." Not only will he refrain from telling a conscious lie of any kind but he will not, through bragging vanity, exaggerate the truth into a half-lie. Any tendency in these directions will be crushed as soon as he becomes aware of it. He will take the trouble to express himself accurately, even to the point of making a fad of the careful choice of his words. Let him not maim his heart nor deform his mind by formulating thoughts which are false. If philosophy be the quest of ultimate truth, then it is certain that such a quest cannot be carried to a successful conclusion if this rule be broken. He who seeks truth must speak it.
-- Notebooks Category 6: Emotions and Ethics > Chapter 1: Uplift Character > # 511