The Holy Prophet (peace and blessings of Allah be upon him) was very strict in his standards of truthfulness, that is why, even before his prophethood, he was popularly known among the people as “The Truthful and Trust Worthy.” In the same way he was equally anxious that Muslims should adopt the same standards of truth as were observed by him. He regarded truth as the basis of all virtue, goodness and right conduct. He taught that a truthful person is the one who is so confirmed in truth that he is counted truthful by God.
On one occasion a prisoner was brought to the Holy Prophet (peace and blessings of Allah be upon him) who had been guilty of the murder of many Muslims. ‘Umar, who was also present, thought that the man deserved the death penalty and he looked repeatedly at the Prophet expecting that the Prophet would at any moment indicate that the man should be put to death. After the Holy Prophet (peace and blessings of Allah be upon him) had dismissed the man, ‘Umar said that he should have been put to death as that was the only appropriate penalty. The Prophet replied, “If that is so, why did you not kill him?”
‘Umar replied, “O Messenger of Allah! If you had but given me an indication even by a flicker of your eye, I would have done so.” To this the Holy Prophet (peace and blessings of Allah be upon him) said: A Prophet does not act equivocally. How could I have employed my eye to indicate the imposition of a death penalty upon the man while my tongue was employed in talking kindly to him? (Hisham)