Commentary: Siddiq (veracious) and Kadhdhab (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.