On the authority of Abu Hurayrah, who said: The Messenger of Allah, peace and blessings be upon him, said: "Whoever comes to the mosque for something, that is his portion."(1)

‌‌21 - Chapter: On the Disapproval of Proclaiming a Lost Item in the Mosque

473 - We were told by ʿUbayd Allah ibn ʿUmar al-Jushamī, we were told by ʿAbd Allah ibn Yazīd, we were told by Ḥaywah ibn Shurayḥ, who said: I heard Abu al-Aswad say: ʿAbd Allah, the freed slave of Shaddād, told me that he heard Abu Hurayrah say: I heard the Messenger of Allah, peace and blessings be upon him, say: "Whoever hears a man proclaiming a lost item in the mosque, let him say: 'May Allah not return it to you,' for the mosques were not built for this."(2)

22 - Chapter: On the Disapproval of Spitting in the Mosque

474 - We were told by Muslim ibn Ibrāhīm, we were told by Hishām, Shuʿbah, and Abān, on the authority of Qatādah--------------------------------------------
(1) Its chain of transmission is weak due to the weakness of ʿUthmān ibn Abī al-ʿĀtikah al-Azdī, and al-Mundhirī deemed it weak on that basis in "Mukhtaṣar al-Sunan."
It was also recorded by al-Bayhaqī 2/447 and 3/66 via the author's chain of transmission.
It was also recorded by Abu Nuʿaym in "al-Ḥilyah" 5/195 via Hishām ibn ʿAmmār, through him.
His saying: "Whoever comes to the mosque for something," meaning: intending to obtain something of the Hereafter or of this world, "that is his portion," meaning: that thing is his portion and share, like his saying, peace be upon him: "Indeed, every person gets only what he intended."
This was stated by the author of "ʿAwn al-Maʿbūd."

(2) Its chain of transmission is authentic. ʿUbayd Allah ibn ʿUmar al-Jushamī: he is al-Qawārīrī. And Abu al-Aswad: he is Muḥammad ibn ʿAbd al-Raḥmān ibn Nawfal.
It was also recorded by Muslim (568), and Ibn Mājah (767) via Ḥaywah ibn Shurayḥ, through this chain of transmission.
It was also recorded by al-Tirmidhī (1321), and al-Nasāʾī in "al-Kubrā" (9933) via Muḥammad ibn ʿAbd al-Raḥmān ibn Thawbān, on the authority of Abu Hurayrah.
It is also in "Musnad Aḥmad" (8588), and "Ṣaḥīḥ Ibn Ḥibbān" (1650) and (1651).
And see the benefits derived from this ḥadīth in "Sharḥ Muslim" 5/46 by Imam al-Nawawī.