Truth leads to piety
Abdullah bin Mas’ud (radi Allahu anhu) reported that The Prophet (sal Allahu alaihi wa sallam) said, “Truth leads to piety and piety leads to Jannah. A man persists in speaking the truth till he is enrolled with Allah as a truthful. Falsehood leads to vice (Immoral or wicked behaviour) and vice leads to the Fire, and a person persists on telling lies until he is enrolled as a liar”
Siddiq (truthful) and Kathaab (liar) both are adjectives of intensive degree. That is to say, the words stand respectively for someone whose truth has become his second nature; and in the opposite case, one is a liar who is in the habit of telling lies.
As one acquires a reputation in this world for his good or bad deeds similar is his position before Allah. One who is ranked among the truthful with Him is entitled to reward, and if one is a liar, he has to suffer retribution for it.
This Hadith provides incentive for truthfulness because it is a source of every good deed and contains a warning against lying as it gives rise to all kinds of mischief.
And Allah Knows Best!