Kitāb-ut-Tawheed : Chapter 2:
وعن أبي سعيد الخدري رضي الله عنه عن رسول الله صلى الله عليه وسلم قال: (قال موسى: يا رب، علمني شيئاً أذكرك وأدعوك به. قال: يا موسى: قل لا إله إلا الله. قال: يا رب كل عبادك يقولون هذا. قال: يا موسى، لو أن السموات السبع وعامرهن غيري، والأرضين السبع في كفة، ولا إله الله في كفة، مالت بهن لا إله الله) [رواه ابن حبان، والحاكم وصححه].
Abu Sa’id Al-Khudri (radi Allaahu anhu) narrated that Allah’s Messenger (sallAllaahu `alayhi wa sallam) said:
“Musa (Moses) (May the peace and blessing of Allah be upon him) said: ‘O my Rabb, teach me something through which I can remember You and supplicate to You.’
Allah answered: ‘Say, O Musa, La ilaha ilIa-Allah‘.
Musa said: ‘O my Rabb, all your slaves say these words’.
Allah said: ‘O Musa, if the seven heavens and all they contain other than Me  (Ghairy) and the seven earths as well, were all put in one side of a scale and La ilaha ilIa-Allah put in the other the latter would overweigh them.'” 
[This Hadith has been reported by Ibn Hibban, and Al-Hakim declared it Sahih].
 This phrase (Ghairy) is the exception from what is in the heavens. It should not be misunderstood that Allah is contained within the heavens or earth since He has described Himself in the Qur’an as the Transcendent, Most High, Above All, i.e. in 2:255, 20:5, 25:59 and many places elsewhere in His Book. Indeed the statement is another proof that Allah cannot be considered within the creation.
[Translation and Footnotes  are taken from: Darusalam english publication]
 This ḥadīth was recorded by Ibn Ḥib-bān, al-Ḥākim, an-Nasā’ī in al-Yawm wal-Laylah, aṭ-Ṭabarānī in ad-Du’ā and al-Bayhaqī in al-Asmā’ waṣ-Ṣifāt. Al-Ḥākim graded it ṣaḥīḥ and ath-Thahabī was silent about it, usually indicating his approval. Similarly Ibn Ḥajar graded it ṣaḥīḥ in Fat.ḥ al-Bārī 11:208, it has a slightly different chain of narrators with aṭ-Ṭabarānī and Abū Ya’la about which al-Haythamī said (al-Majma’): “It is recorded by Abū Ya’la and its men are trustworthy, but among them there is some weakness.” Commenting on the chain of Ibn Ḥib-bān, ‘Alūsh (Tashnif al-Athān no. 927) says: “Its chain is weak, Darāj Abū Sumah is weak in his reports from Abū al-Haytham.” Ibn al-Munthir listed Darāj Abū Sumah among the narrators who the ḥadīth scholars differ over saying, “Abū Ḥātim declared him weak, as did ad-Dāraqutnī and others, Aḥmad said, “His ḥadīths are rejected,” an-Nasā’ī said, “Rejected.” Yet others considered him trustworthy like Yahyā b. Ma’īn (it seems that quotes from him are what al-Ḥākim depended upon according to al-Munthirī’s comments in at-Targhīb) and particularly at-Tirmithī in case he reports from Abū al-Haytham (as in this case)! Likewise he was quoted for support by Ibn Khuzaymah. Al-Albānī calls him the possessor and author of munākir (rejected ḥadīths) see al-Dā’īfah 1:294 and 254. Al-Albānī graded it weak in Da’īf al-Mawārid al-Zamān no. 295 , as did Muqbil b. Hādī in al-Mustadrak no. 1988.
There is however a more agreed upon authentic ḥadīth with different wording that gives much of the desired meaning for the context of this point. ‘Abdullāh b. ‘Amr b. al-‘Ās narrated that the Prophet (sallAllaahu `alayhi wa sallam) said: «When death visited Allah’s Prophet Nūh (alaihissalam), he said to his son: “I shall narrate to you the will. I command you with two things and I forbid you from two things: I command with Lā ilāha illa Allāh. Surely if the seven heavens and the seven earths were placed on a pan of a scale, and Lā ilāha illa Allāh was placed on the other pan of the scale, they would give in to Lā ilāha illa Allāh…» This ḥadīth was recorded by al-Bukhaaree in al-Adab al-Mufrad, Aḥmad, al-Bayhaqī in al-Asmā’, and also aṭ-Ṭabarānī according to al-Haythamī who said, “This isnād is ṣaḥīḥ.” Al-Albānī included it in aṣ-Ṣahīhah no. 134, and Shaykh Muqbil b. Hādī included Aḥmad’s ḥadīth in Ṣaḥīḥ al-Musnad minma Laysa fī aṣ-Ṣaḥīḥayn v. 1 p.544 and he said, “This ḥadīth is ṣaḥīḥ.”
[Footnote 02 is taken from English Publication of “Explanation of Kitab at-Tawheed” by Imam as-Sa’di]
Extracted From: Kitāb-ut-Tawheed – Dawud Burbank [Audio Series|En]
Mainly based upon Imam AbdurRahman Al-Sadi’s explanation, which can be used as study aid while listening to the series. In addition, Dawud Burbank rahimahullaah also explains some Points from Shaykh Uthaymeen and other Imaams as well.
Kitāb at-Tawheed Book Study – https://abdurrahman.org/islamic-book-study/kitab-at-tawheed