Well this Hadith could be found in many Hadith collections:
- like sahih al-Bukhari where "will be forgiven" is referred to (in Arabic) by معافى which regard the Ummah or all the followers of the Messenger of Allah (peace be upon him) as a masculin plural (which is the most used version in other hadith collections). In some narrations of sahih al-Bukhari you may find instead of the mansob version "الْمُجَاهِرِينَ" (al-Mujahirin) the marfo' "الْمُجَاهِرُونَ" (al-Mujahiron) which is the version of an-Nasafi and correct Arabic according the al-Kufa school (but worng accoring al-basra school).
- sahih Muslim where "would get pardon" is referred to (in Arabic) by معافاة which consider the Ummah or the followers of the Messenger of Allah (peace be upon him) as a feminin singular.
- Abu Na'im also quoted it in his book hilyat al-awliya' حلية الأولياء 2/255 (you could use this linked site to check the narrator chains if you are able to read Arabic) with a different statement:
إن من شرار الناس المجاهرين. قالوا : يا رسول الله ! وما المجاهرون ؟ قال : الذي يذنب الذنب بالليل فيستره الله عليه ، فيصبح فيحدث به الناس فيقول : فعلت البارحة كذا وكذا فيهتك ستر الله عنه
(My translation so take it with care)
Among the worst people are those who publicise, they Asked: o Messenger of Allah! And who are those who publicise? He said: (it means) that is a servant who does a bad deed during the night whereas Allah concealed it, and in the morning he tells the people about it and says: Yesterday i did such and such. So he disclose the cover of Allah from him.
- And others like al-Bayhaqi, ibn Al-A'rabi, ibn al-Bzaz, ibn 'abd al-Barr ... (A complete list in Arabic see here)
All these more or less different narrations have been narrated on the authority of abu Huraira (=Abdullah ibn Sakhr عبد الرحمن بن صخر ) (May Allah be pleased with him)!
Just to check the authenticity again here i will go through the narrator chains of the 3 linked narrations:
- In sahih al-Bukhari the chain goes as follows:
Abdulaziz ibn Abdullah (Al-Awaysi) عَبْدُ الْعَزِيزِ بْنُ عَبْدِ اللَّهِ: Trustworthy ثقة
Ibrahim ibn Sa'ad (Az-Zuhari) إِبْرَاهِيمُ بْنُ سَعْدٍ: Trustworthy, authority ثقة حجة
The son of the brother of ibn Shihab (Mohammad ibn Abdullah az-Zuhari) ابْنِ أَخِي ابْنِ شِهَابٍ: Was considered as trustworthy to some extent as he had some "fantasy's" صدوق له أوهام
Ibn Shihab (also known as "Az-Zuhari") ابْنِ شِهَابٍ: is a well known Muhadith and Scholar (he was asked to collect ahadith by the khalifa 'Omar ibn Abdulaziz) he is trustworthy, if his hadith has a sanad (he used to do marasil=jumping some of the rawys)!
Salim ibn Abdullah (also known as salim ibn Abdullah al-'Adawy) سَالِمِ بْنِ عَبْدِ اللَّهِ: he is known to be trustworthy ثقة and certain (doesn't mix or forget) ثبت
- In sahih Muslim the chain goes as follows (the 3 first narrators narrated from the 4th one and afterwards the chain is the same as in sahih al-Bukhari):
Zohayr ibn Harb (al-Harshi) زُهَيْرُ بْنُ حَرْبٍ: trustworthy and certain ثقة ثبت
Mohammad ibn Hatem (as-Samyn) مُحَمَّدُ بْنُ حَاتِمٍ: he used to tell the truth but had apparently fantasy's, was a nobel man صدوق ربما وهم وكان فاضلا, Yahya ibn Ma'yn said he was a liar!
'Abd ibn Humayd (al-Kashi or al-Koshi) عَبْدُ بْنُ حُمَيْدٍ : trustworthy and had a good memory ثقة حافظ
Ya'qob ibn Ibrahim (al-Qurashi) يَعْقُوبُ بْنُ إِبْرَاهِيمَ: trustworthy ثقة
->Ibrahim ibn Sa'ad (Az-Zuhari)->The son of the brother of ibn Shihab->
Ibn Shihab -> Salim ibn Abdullah (see the chain of al-Bukhari)
- In hilyat al-awliya' the chain goes as follows:
Solayman ibn Ahmad (At-Tabarani) سُلَيْمَانُ بْنُ أَحْمَدَ: Imam trustworthy with a good memory and an author of many ahadith collections
'Ali ibn Abdulaziz (Ibrahim ibn 'isa al-'Absy) عَلِيُّ بْنُ عَبْدِ الْعَزِيزِ: unknown
'Obayd ibn Y'iych (al-Mahlami) عُبَيْدُ بْنُ يَعِيشَ: trustworthy, ibn Hiban said he made some mistakes
Abu Bakr ibn 'Ayyach (Al-Assadi) أَبُو بَكْرِ بْنُ عَيَّاشٍ: sadoq صدوق and hasan al hadith حسن الحديث : he used to do mistakes most scholars because he seem to have a bad memory and used to mix when he became older but all agree that he was not a liar or a fabricator!
Mobashshir مُبَشِّرٍ: I couldn't find him!
(Ibn Shihab) Az-Zuhari -> Salim ibn Abdullah (See the chain from sahih al-Bukahri)
The chains of the both sahih books have a very high level of authenticity!
And Allah knows best!