Ibn Majah

Commentary:

➊
This narration is mawquf, meaning it is the statement of a Companion and not the saying of the Prophet sallallahu alayhi wa sallam. However, the virtue and importance of the siwak (tooth-stick) is established from marfu‘ (Prophetic) ahadith.

➋
The meaning of “your mouths are the pathways of the Qur’an” is clarified by another narration, according to which, when a person recites the Qur’an, an angel comes and stands behind him, and as the recitation continues, the angel draws so near that it places its mouth upon the mouth of the reciter. Then, whatever verse the reciter utters enters into the angel. Therefore, it is said that one should keep the mouth clean while reciting the Qur’an.
(al-Sahihah, Hadith: 1213)
On the basis of this narration, Shaykh al-Albani has also authenticated it. In any case, the respect due to the Noble Qur’an demands that the mouth be kept pure and clean.

➌
The requirement to keep the mouth clean also entails avoiding foul-smelling substances. The Messenger of Allah sallallahu alayhi wa sallam would avoid onions and the like, even though they are not unlawful; thus, it is even more necessary to avoid intoxicants, as they are both unlawful and foul-smelling.
Cigarettes and tobacco and the like are also extremely foul-smelling substances, and they have no benefit, while their harms are numerous. Therefore, their use falls under the category of wasteful expenditure, regarding which Allah the Exalted has stated:
﴿وَلَا تُبَذِّرْ تَبْذِيرًاO إِنَّ الْمُبَذِّرِينَ كَانُوا إِخْوَانَ الشَّيَاطِينِ ۖ وَكَانَ الشَّيْطَانُ لِرَبِّهِ كَفُورًا﴾ (Bani Isra’il: 27, 26: 17)
“And do not spend wastefully. Indeed, the wasteful are brothers of the devils, and ever has Satan been to his Lord ungrateful.”
In the same way, it is necessary to keep the mouth pure from abusive language, obscene speech, lying, deception, and other such acts.