Note: The text between the square brackets had dropped out of the manuscripts here, and the author's words after it require that it be present.
Technical note: The one who narrates from Muhammad al-Kinani is "Muhammad al-Dhuhli", not Abu Hatim, as stated in the books of narrator biographies.

Grading: A sahih hadith.
Technical note: This chain is "jayyid" (good) on account of Abd al-Aziz al-Darawardi.

Reference / Source: Al-Bayhaqi (8/21) narrated it via Ahmad bin Muhammad bin al-Hasan al-Hafiz, from Muhammad bin Yahya al-Dhuhli, with this same chain.

Reference / Source: Al-Tabarani narrated it in "al-Awsat" (1401) via Ahmad bin Shabbawayh al-Marwazi, from Abu Ghassan Muhammad bin Yahya al-Kinani, with this same chain.

Note: See the narration after it.

Meanings of the hadith: Regarding the words "fi fushah min dinihi" (he remains in latitude within his religion), Ibn al-Arabi said (as al-Hafiz Ibn Hajar quoted from him in "Fath al-Bari" 22/8): "Latitude (fushah) in religion means the breadth of righteous deeds, until, when killing comes, it becomes narrow, because the deeds cannot make up for its burden. And latitude in sin means the acceptance of forgiveness through repentance, until, when killing comes, acceptance is lifted."
Summary: The upshot is that he interpreted it according to the view of Ibn Umar (may Allah be pleased with them both) that the repentance of a killer is not accepted.

Corroboration: It has passed in the sources that Ahmad bin Shabbawayh al-Marwazi corroborated al-Dhuhli in this narration.