Zuhayr reported it as a saying of Ibn ʿAbbās (mawqūf):

1703 — Aḥmad ibn Sulaymān informed us, saying: Abū Nuʿaym narrated to us, saying: Zuhayr narrated to us, from Abū Isḥāq, from Saʿīd ibn Jubayr, from Ibn ʿAbbās, that he used to perform the Witr with three [units], reciting: {Glorify the name of your Lord, the Most High} and {Say: O disbelievers} and {Say: He is Allah, the One}.

39 — Mention of the discrepancy concerning Ḥabīb ibn Abī Thābit regarding the ḥadīth of Ibn ʿAbbās on the Witr

1704 — Muḥammad ibn Rāfiʿ informed us, saying: Muʿāwiyah ibn Hishām narrated to us, saying: Sufyān narrated to us, from Ḥabīb ibn Abī Thābit, from Muḥammad ibn ʿAlī, from his father, from his grandfather, from the Prophet ﷺ, that he rose during the night, used the toothstick (istākka), then prayed two units, then slept, then rose and used the toothstick, then performed ablution and prayed two units, until he had prayed six, then he performed the Witr with three, and prayed two units.

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All three of them [narrated] from Abū Isḥāq, with this chain of transmission.
Aḥmad (2776) also recorded it via the path of Muslim ibn ʿImrān al-Baṭīn, from Saʿīd ibn Jubayr, from him.
And Zuhayr ibn Muʿāwiyah alone reported it as a saying of Ibn ʿAbbās (mawqūf), as in the following narration.

(1) Authentic as raised to the Prophet (marfūʿ), and this chain's narrators are trustworthy, except that Zuhayr — namely Ibn Muʿāwiyah al-Juʿfī — alone reported it as a saying of Ibn ʿAbbās, and he heard from Abū Isḥāq al-Sabīʿī late in his life. Abū Nuʿaym: he is al-Faḍl ibn Dukayn. It is in "al-Sunan al-Kubrā" under number (1432).
It has already been transmitted as raised to the Prophet (marfūʿ) in the preceding narration.

(2) Its narrators are trustworthy, except Muʿāwiyah ibn Hishām, for he is ṣadūq (truthful). Sufyān: he is al-Thawrī. It is in "al-Sunan al-Kubrā" under number (1346).
Aḥmad (3271) also recorded it via Muʿāwiyah ibn Hishām, with this chain of transmission. And see the discussion on it in the following ḥadīth.