The Messenger of Allaah (sallal-laahu-alayhi-wasallam) said:

‘Indeed Allaah is Pure and He does not accept, except that which is pure’

Al-Allaamah Saaleh Al Fawzaan (may Allaah preserve him) said:

In this hadith he (sallal-laahu-alayhi-wasallam) described Allaah (جل وعلا) (saying) that Allaah (سبحانه) is Pure.  He (سبحانه) is Pure, meaning: He is free from all imperfections and deficiencies.  He is Pure in His Essence, in His Names and Attributes and with regards to His Commandments and Prohibitions.  He (سبحانه) is Pure in every aspect and imperfection cannot reach Him; and for that reason He does not accept actions, statements and intentions except that which is pure.  He does not accept filthy statements, actions and intentions.  He does not accept except the pure, as He (The Most High) said: [إِلَيۡهِ يَصۡعَدُ ٱلۡكَلِمُ ٱلطَّيِّبُ وَٱلۡعَمَلُ ٱلصَّـٰلِحُ يَرۡفَعُهُۚ  ] ‘To Him ascend (all) the goodly words’[Surah Faatir Ayah: 10]

He (سبحانه) does not accept, except good speech and good actions…up until the Sheikh said: As for filthy speech, then indeed Allaah rejects and hates it; such as lies, backbiting, tale carrying, abuse, false speech and false testimony and all filthy statements; (such as) shirk and kufr.  All of this is filthy speech and does not ascend to Allaah, and is not accepted.

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[Abridged and slightly paraphrased. Source: Al Minhatu Ar-Rabbaaniyyah Fee Sharh Arba-een Nawawiyyah’ page:133-134]