Quran 23:90

This vow, O Partha, was adopted by thee before from foolishness. In consequence of that vow thou art now, from folly, desirous of perpetrating a sinful act. Why, O Partha, dost thou rush towards thy reverend superior for slaying him, without having resolved the exceedingly subtle course of morality that is, again, difficult of being understood? I will now tell thee, O son of Pandu, this mystery connected with morality, this mystery that was declared by Bhishma, by the righteous Yudhishthira, by Vidura otherwise called Kshatri, and by Kunti, of great celebrity. I will tell thee that mystery in all its details. Listen to it, O Dhananjaya! One who speaks truth is righteous. There is nothing higher than truth. Behold, however, truth as practised is exceedingly difficult to be understood as regards its essential attributes. Truth may be unutterable, and even falsehood may be utterable where falsehood would become truth and truth would become falsehood. In a situation of peril to life and in marriage, falsehood becomes utterable. In a situation involving the loss of one's entire property, falsehood becomes utterable. On an occasion of marriage, or of enjoying a woman, or when life is in danger, or when one's entire property is about to be taken away, or for the sake of a Brahmana, falsehood may be uttered. These five kinds of falsehood have been declared to be sinless. On these occasions falsehood would become truth and truth would become falsehood. He is a fool that practises truth without knowing the difference between truth and falsehood. One is said to be conversant with morality when one is able to distinguish between truth and falsehood. What wonder then in this that a man of wisdom, by perpetrating even a cruel act, may obtain great merit like Valaka by the slaughter of the blind beast? What wonder, again, in this that a foolish and ignorant person, from even the desire of winning merit, earns great sin like Kausika (living) among the rivers?"

It has brown ears; that is the symbol of the Brahman; (verily it serves) for prosperity. The sacrificial post is shaped like the wooden sword; the wooden sword is a thunderbolt; verily he hurls a thunderbolt against him; the strew is made of Çara grass; verily he crushes [2] him; the kindling-wood is of Vibhidaka; verily he splits him. He to whom the sacrifice does not come should offer a dwarf (beast) to Visnu; the sacrifice is Visnu; verily he has recourse to Visnu with his own share; verily he gives him the sacrifice, the sacrifice comes to him. It is a dwarf (beast), for it has Visnu for its deity; (verily it serves) for prosperity. He who desires cattle should offer to Tvastr a horse; Tvastr is the producer of pairings of animals [3]; verily he has recourse to Tvastr with his own share; verily he produces animals in pairs for him, for in him offspring and cattle have entered; verily also the male horse straightway wins offspring and cattle. He who when a contest is joined desires an agreement should offer to Mitra a white (beast); verily he has recourse to Mitra with his own share; verily he brings him into harmony with his friend [4]. It is spacious; verily he encourages him. He who desires rain should offer to Prajapati a black (beast), Prajapati is the lord of rain; verily he has recourse to Prajapati with his own share; verily he makes Parjanya rain for him. It is black, that is the form of rain; verily by its form he wins rain. It is spotted; verily he produces the lightning and makes rain for him. It has low horns; verily he brings down the rain for him. Food came not to Varuna when he had pressed. He beheld this black cow which is Varuna's; it he offered to its own deity; then food came to him. He to whom being fit for food food does not come should offer to Varuna this black cow; verily he has recourse to Varuna with his own form; verily he gives him food; he becomes an eater of food [1].

They who know truth in truth, and untruth in untruth, arrive at truth, and follow true desires.

Sanctify them through thy truth: thy word is truth.