Bukhari

Hadith Commentary:
The narration from Isma'il ibn Abi Khalid that has been transmitted in the chain has been connected by Husayn Marwazi in the "Ziyadat al-Zuhd." However, in the "Ziyadat," he first narrated this report as mawquf (stopped) from Rabi'. At the end of it, it is stated:

Sha'bi said: I asked Rabi', "From whom did you hear this?" He replied, "From Amr ibn Maymun."
I met him and asked, and he said, "I heard it from Abdur Rahman ibn Abi Layla."
I met him and asked, "From whom do you narrate this hadith?" He said, "From Abu Ayyub Ansari radi Allahu anhu, who narrated it from the Messenger of Allah sallallahu alayhi wa sallam."
The phrase "La ilaha illallah wahdahu la sharika lahu..." is a statement of great virtue.

In some narrations, after "walahu al-hamd," the words "yuhyi wa yumit" are added, and in some, the words "ghayruka" etc. are also found as additions.

This phrase is the greatest elixir for sinners.
If one recites this phrase at least one hundred times daily, then in addition to being an expiation for sins, one's belief in tawhid (the oneness of Allah) will become so strong and firm that, due to the blessing of tawhid, the person will feel a special strength of faith within himself.

The humble writer, servant Muhammad Dawud Raz, in his insignificant lifetime, has had the honor of meeting many such elders whose strength of faith I could not estimate.
Among them was the famous elder of Bombay, the emigrant to Makkah, Hazrat Haji Munshi Aleemullah Sahib, who now rests in the land of Makkah itself.
May Allah forgive him and admit him to Jannat al-Firdaws.
Amin.

The narration of Abu Muhammad Hadrami has been connected by Imam Ahmad and Jurjani.
In some copies, there is an additional phrase here: "Qala Abu Abdillah wa al-sahih qawl Amr," meaning Hazrat Imam Bukhari said that the narration of Amr is correct, although above, there is no narration of Amr, rather it is of Amr ibn Zaydah.

Hafiz Abu Dharr said: "'Amr' without a waw is correct."

Hadith Commentary:
(1)
This statement of Tawheed (the declaration of Allah’s oneness) serves as the greatest elixir for sinners like us. If one recites this statement at least one hundred times a day, not only will it serve as an expiation for sins, but the belief in Tawheed will become so strong that the one who recites it will feel a special strength of faith due to the blessings of Tawheed. Hafiz Ibn Hajar rahimahullah says: In some narrations, it is mentioned that whoever performs this practice in the evening will also receive the same reward.

(2)
The apparent meaning of the hadith indicates that this reward will be granted to every person who makes this practice a regular part of his life, whether he recites it continuously or intermittently, in intervals. Whether he recites it at the beginning of the day or at the end of the day, but it is better to recite this statement one hundred times consecutively at the start of the day so that he remains protected from Satan throughout the day. Similarly, he should repeat this practice at the beginning of the night so that he remains safe from satanic influences throughout the night. (Fath al-Bari: 11/246)

(3)
According to our inclination, the prescribed (masnun) remembrances (adhkar) contain such blessings and benefits that there is absolutely no need to add further remembrances to them; moreover, self-invented remembrances are not a means of reward. In a hadith narrated from Abu Sa’id al-Khudri radi Allahu anhu, this practice is mentioned after the morning prayer, and in it, the phrase “biyadihi al-khayr” is added. (Sunan Ibn Majah, al-Adab, Hadith: 3799) However, its chain of narration is weak due to Atiyyah al-Awfi. And Allah knows best.