His saying, (The Mighty and The Majestic): speak (always) the truth, Ibn Katheer said commenting upon this: “Meaning: (speech) that is sound, containing no crookedness and no distortion. Allaah promised them if they were to do this He would reward them by rectifyingtheir actions. This means that He would forgive their past sins; and if anything occurs from them in the future He will inspire them to repent.” 

He, the Most High, said:

Not a saying (qawl) does he (or she) utter, but there is a watcher by him ready (to record it). [Soorah Qaaf (50):18]

The word 'Qawl’ (in this verse) is in the indefinite form; and when an indefinite word comes in the course of a negation it conveys a general and all-inclusive meaning. On top of that, if the word “min” comes before it, it is even greater in generality.

Some of the scholars stated:
“None of the actions are recorded unless they warrant a reward or a punishment, and this is because there is an omission of words which has been implied (in meaning). Therefore, it means: ‘Not a word does he utter that is worthy of deserving recompense.’

The base rule is that there is no omission. So the verse is to be understood with its apparent meaning, in that it is general and applies to all kinds of speech.” Refer to ‘Adwaa al-Bayaan (7/651):

Many of the women today move their tongues loosely when speaking, as if she doesn’t know that she will be brought to account for her actions and speech. If they (actions and speech) were evil, then she will be rewarded with evil. If they (actions and speech) were good, then she will be rewarded with good.

Al Haakim reports in his book ‘Al Mustadrak’ upon the authority of ‘Ubaadah Ibn As-Saamit (radiyallaahu anhu) that the Prophet (Salla Allaahu ‘Alayhi wa sallam) pointed to his mouth and said:

“Silence brings nothing but good.” Mu’aadh (Radiy Allaahu anhu) said to him: “Will we be held to account for that which we speak with our tongues?”
The Prophet (Salla Allaahu ‘Alayhi wa sallam) (upon hearing this) hit Mu’aadh’s thigh and said, “O Mu’aadh! May your mother be bereaved of you,” or he said: "Maasha Allaah," that he said this to him. He (Salla Allaahu ‘Alayhi wa sallam) said: “Is there anything that causes the people to be dragged on their nose to the Hellfire except that which their tongues uttered? So he who believes in Allaah and the Last Day then let him speak good or remain silent (refrain from evil speech). Speak good - you will benefit; remain silent - you will be safe.” - This hadeeth is authentic, as mentioned in ‘As Saheeh al Musnad’. (1/400)

Allaah said:
"So whosoever does good equal to the weight of an atom (or a small ant), shall see it. And whosoever does evil equal to the weight of an atom (or a small ant), shall see it." [Soorah Az-Zalzalah (99):7-8]

Also, speech is considered to be part one’s actions. Allaah, the Most High, said:

And say (O Muhammad) "Do deeds! Allâh will see your deeds, and (so will) His Messenger and the believers. And you will be brought back to the All-Knower of the unseen and the seen. Then He will inform you of what you used to do." [Soorah At-Tawbah (9):105]

‘Umar Ibn ‘Abdul ‘Azeez said, as is reported in ‘Jaami’ al-Uloom’ of Ibn Rajab page 114: "Whoever recognises that his speech is part of his actions would speak little, and only in that which concerns him.”

So congratulations are in order for the one who fills his Record with good and righteous actions, and misery to the one who fills his Book with worthless speech and evil actions.

He, the Most High, said:

Then as for him who will be given his Record in his right hand, he will say: "Take, read my Record! Surely, I did believe that I shall meet my Account!" So he shall be in a life, well-pleasing. In a lofty Paradise, the fruits in bunches whereof will be low and near at hand. Eat and drink at ease for that which you have sent on before you in days past! [Soorah Al-Haqqah (69):19-24]

And He, the Most High, said:

But as for him who will be given his Record in his left hand will say: "I wish that I had not been given my Record! And that I had never known how my Account is? I wish, would that it had been my end (death)! My wealth has not availed me, my power and arguments (to defend myself) have gone from me!" (It will be said): "Seize him and fetter him, then throw him in the blazing Fire. Then fasten him with a chain whereof the length is seventy cubits!" Verily, He used not to believe in Allâh, the Most Great, And urged not on the feeding of Al-Miskîn (the poor), So no friend has he here this Day, nor any food except filth from the washing of wounds, none will eat except the Khâti'ûn (sinners, disbelievers, polytheists, etc.). [Soorah Al-Haqqah (69):25-37]

(Bearing that in mind) which of the two groups do you want to be from? There is no doubt that you will reply, "I wish to be from the People of Paradise.” Therefore, don’t allow your tongue to bring your destruction.

The fact that actions are recorded does not mean that if they were not recorded that Allaah would not know about them; for verily nothing is hidden from Allaah. As Allaah, the Most High, said:

And with Him are the keys of the Ghaib (all that is hidden), none knows them but He. And He knows whatever there is in (or on) the earth and in the sea; not a leaf falls, but he knows it. There is not a grain in the darkness of the earth nor anything fresh or dry, but is written in a Clear Record. [Soorah Al-An'aam (6):59]

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