Regarding the hadeeth:

Salim bin Abdullah bin Umar narrated from his father, from his grandfather, that :
the Messenger of Allah (ﷺ) said:

“Whoever enters the marketplace and says: ‘There is none worthy of worship except Allah, Alone, without partner, to Him belongs the dominion, and to Him is all the praise, He gives life and causes death, He is Living and does not die, in His Hand is the good, and He has power over all things, (Lā ilāha illallāh, waḥdahu lā sharīka lahu, lahul-mulku wa lahul-ḥamdu, yuḥyī wa yumītu, wa huwa ḥayyun lā yamūtu, biyadihil-khairu, wa huwa `alā kulli shay’in qadīr)’ Allah shall record a million good deeds for him, wipe a million evil deeds away from him, and raise a million ranks for him.”

حَدَّثَنَا أَحْمَدُ بْنُ مَنِيعٍ، حَدَّثَنَا يَزِيدُ بْنُ هَارُونَ، أَخْبَرَنَا أَزْهَرُ بْنُ سِنَانٍ، حَدَّثَنَا مُحَمَّدُ بْنُ وَاسِعٍ، قَالَ قَدِمْتُ مَكَّةَ فَلَقِيَنِي أَخِي سَالِمُ بْنُ عَبْدِ اللَّهِ بْنِ عُمَرَ فَحَدَّثَنِي عَنْ أَبِيهِ عَنْ جَدِّهِ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ “‏ مَنْ دَخَلَ السُّوقَ فَقَالَ لاَ إِلَهَ إِلاَّ اللَّهُ وَحْدَهُ لاَ شَرِيكُ لَهُ لَهُ الْمُلْكُ وَلَهُ الْحَمْدُ يُحْيِي وَيُمِيتُ وَهُوَ حَىٌّ لاَ يَمُوتُ بِيَدِهِ الْخَيْرُ وَهُوَ عَلَى كُلِّ شَيْءٍ قَدِيرٌ كَتَبَ اللَّهُ لَهُ أَلْفَ أَلْفِ حَسَنَةٍ وَمَحَا عَنْهُ أَلْفَ أَلْفِ سَيِّئَةٍ وَرَفَعَ لَهُ أَلْفَ أَلْفِ دَرَجَةٍ ‏”‏ ‏.‏ قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ غَرِيبٌ ‏.‏
وَقَدْ رَوَاهُ عَمْرُو بْنُ دِينَارٍ – وَهُوَ قَهْرَمَانُ آلِ الزُّبَيْرِ عَنْ سَالِمِ بْنِ عَبْدِ اللَّهِ، هَذَا الْحَدِيثَ نَحْوَهُ.

Grade : Da’if (Darussalam)
Reference : Jami` at-Tirmidhi 3428″

[Reference]

There is a difference of opinion among the Scholars but a group of them authentic it. Like Imam al-Albani (may Allah have mercy upon him) [Saheeh at-Targheeb no. 1694]

Shaikh Yahya (may Allah preserve him) said in his Commentary on The Means and Actions which Multiply Rewards Part 3, which we studied and translated:

“This is also good speech. It is correct. How many people are in the places of business and the people are busy with their wealth etc. and he makes remembrance of Allah. The virtue of this comes in the dhikr in the market:

مَنْ قَالَ فِي السُّوقِ لاَ إِلَهَ إِلاَّ اللَّهُ وَحْدَهُ لاَ شَرِيكَ لَهُ لَهُ الْمُلْكُ وَلَهُ الْحَمْدُ يُحْيِي وَيُمِيتُ وَهُوَ حَىٌّ لاَ يَمُوتُ بِيَدِهِ الْخَيْرُ وَهُوَ عَلَى كُلِّ شَيْءٍ قَدِيرٌ كَتَبَ اللَّهُ لَهُ أَلْفَ أَلْفِ حَسَنَةٍ وَمَحَا عَنْهُ أَلْفَ أَلْفِ سَيِّئَةٍ وَبَنَى لَهُ بَيْتًا فِي الْجَنَّةِ

Whoever states in the marketplace: ‘There is none worthy of worship except Allah, Alone, without partner, to Him belongs the dominion, and to Him is all the praise, He gives life and causes death, and He is Living and does not die, in His Hand is the good, and He has power over all things, Allah shall record a million good deeds for him, wipe a million evil deeds away from him, and build a house in Paradise for him [Saheeh Targheeb no. 1694 ]

An author has written a treatise entitled “The Trustworthy Statement in Regards to the Authentication of the Hadith of the Market (القول الموثوق في تصحيح حديث السوق)”
[Footnote: This book was written by Shaikh Saleem bin ‘Eid al-Hilali (may Allah preserve him)]

The hadith with all its routes is Hasan”

Shaikh Saleem al-Hilali (may Allah preserve him) concluded that it is Saheeh as in the above book “The Trustworthy Statement in Regards to the Authentication of the Hadith of the Market (pg. 89)”

And Allah Knows Best

Faisal bin Abdul Qaadir bin Hassan
Abu Sulaymaan