Grading: Its chain is weak because it is broken (munqati');
Technical note / Defect ('illah): for Ma'mar did not hear this hadith from Sa'id al-Maqburi; between them there is an unnamed intermediary, and Imam al-Tirmidhi pointed to this, as will come.

Reference / Source: Ibrahim al-Harbi recorded it in "al-Gharib" (642) and Abu Ya'la (6542) from Muhammad bin Abd al-Rahman bin Sahm al-Antaki, from Abdullah bin al-Mubarak, from Ma'mar, from Sa'id al-Maqburi, from his father, from Abu Hurayrah.
Technical note / Defect ('illah): So he added in it the father of Sa'id al-Maqburi (Abu Sa'id al-Maqburi).

Reference / Source: This hadith is in Ibn al-Mubarak's "al-Zuhd" (7) from Ma'mar, (in the words:) "from someone who heard al-Maqburi narrating from Abu Hurayrah". Likewise it was narrated through his route by Hannad in "al-Zuhd" (504), Ibn Abi al-Dunya in "Qisar al-Amal" (110), al-Bayhaqi in "Shu'ab al-Iman" (10089), al-Quda'i in "Musnad al-Shihab" (823) and Abu Muhammad al-Baghawi in "Sharh al-Sunnah" (4022).
Note / Clarification: A mistake occurred in the narration of al-Quda'i.

Reference / Source: Al-Tabarani recorded it in "al-Awsat" (3945) and al-Khatib in "al-Sabiq wa al-Lahiq" (pp. 107-108) via Ibrahim bin A'yan, from Ma'mar, from Muhammad bin 'Ajlan, from Sa'id al-Maqburi, from Abu Hurayrah.

Note / Clarification: He said: No one narrated this hadith from Muhammad bin 'Ajlan except Ma'mar, nor from Ma'mar except Ibrahim bin A'yan, nor from Ibrahim except Isra'il, nor from Isra'il except Ibrahim bin al-Mukhtar; Muhammad bin Humayd is alone in narrating it.

Grading: We say: Its chain is "musalsal bil-du'afa'" (made up of weak narrators one after another).
Technical note / Defect ('illah): Had it been authentic, we would have known the unnamed intermediary (i.e. we would accept that he is Ibn 'Ajlan).

Reference / Source: Al-Tirmidhi (2306) and others recorded it via Muharrar bin Harun, from al-A'raj, from Abu Hurayrah.
Grading: Al-Tirmidhi said: This hadith is "hasan gharib"; we know it from the narration of al-A'raj from Abu Hurayrah only through Muharrar bin Harun; and Ma'mar narrated something similar to this hadith "from someone who heard Sa'id al-Maqburi", from Abu Hurayrah, from the Prophet (peace and blessings be upon him).
Technical note / Defect ('illah): We say: Muharrar (who is also called Muhriz) is weak and munkar al-hadith.
Reference / Source: Al-Quda'i (824) recorded it via Muhammad bin Ibrahim bin Abi Sukaynah, from Ibn al-Mubarak, from Yahya bin 'Ubaydullah, from his father, from Abu Hurayrah.
Grading: We say: Yahya bin 'Ubaydullah (Ibn Abdullah bin Mawhab) is matruk (abandoned) and his father is majhul (unknown).

Corroborating chains and supporting reports: On this topic there is a report from Abu Umamah in Ibn Abi al-Dunya's "Qisar al-Amal" (203), and through his route in al-Bayhaqi's "al-Shu'ab" (10090). Its wording is: "Hasten to do good deeds before a spoiling old age, or a snatching death, or a confining illness, or a procrastination that leads to despair."
Grading: Its chain is weak.
Technical note / Defect ('illah): The reason is that the status of Yusuf bin Abd al-Samad is unknown, and Muhammad bin Abi Layla is "sayyi' al-hifz" (of poor memory) and did not hear from his Companion Abu Umamah.