Rasul Allah (sal Allahu alaihi wa sallam) said: “Truthfulness leads to righteousness and righteousness leads to Paradise; a person remains truthful until he is written as a Siddeeq (truthful person) with Allah. Lying leads to sin and sin leads to the Fire; a person keeps lying until he is written as a Kadhdhab (liar) with Allah.” [ Bukhari, Muslim ]
Imam Malik records that Abdullah ibn Masud would state, “Each time somebody lies a black spot shows up on his heart until his entire heart winds up dark and he is composed with Allah as a Kadhdhab.”
He additionally records that it was asked of Luqman, “How have you achieved this level in magnificence?” He answered, “By being valid in discourse, satisfying trusts and leaving what does not concern me.” Such is the significance of staying honest that the Prophet (sal Allahu alaihi wa sallam) said that a Mu’min could at any one time perform one sin or the other yet he would never be a liar.
Shaytaan incites us to lie, saying ‘it is just one falsehood’. In any case, that is the manner by which the propensity creates and before an individual knows it, each black speck has had its total impact of darkening the entire heart.
The total blackening of the heart is the confirmation an individual presents to Allah to have that person recorded as a kadhdhab – an affirmed liar.