I say: This is an outright lie and a malicious deception of the readers. Nafi ibn Jubayr was a well-known, trustworthy Successor. Even if he had said, “Its chain is mursal and authentic,” he would still have been lying, for the route to it contains two defects that preclude declaring it authentic.
The first is apparent to everyone acquainted with this field, and I do not suppose that it was unknown to al-Ghumari; rather, it is bias! It lies in Ibn Jurayj’s wording: “He said: Nafi said.” Ibn Jurayj was one of the narrators well known for concealment in transmission and for practising it frequently, as stated in al-ʿAlaʾi’s al-Tahsil (p. 123). A narrator such as him has his hadith accepted only when he explicitly states that he heard it directly—especially since, as al-Daraqutni said: “His concealment in transmission is reprehensible: he practises it only in reports he heard from an impugned narrator, such as Ibrahim ibn Abi Yahya and Musa ibn Ubaydah.”
The other defect is that Abd al-Razzaq recorded it in the Book of Prayer in his al-Musannaf (1/532/2030). This book is transmitted from him by Ishaq ibn Ibrahim al-Dabari (see p. 349 thereof), and there is well-known criticism concerning his hearing it from him. Al-Nasa’i said in al-Duʿafaʾ (p. 297/379), in the biography of Abd al-Razzaq: “There is cause for concern regarding those who recorded from him late in his life.” Al-Tahdhib adds, quoting him: “Rejected hadiths were recorded from him.” Al-Dhahabi said in al-Mizan, in the biography of Ishaq ibn Ibrahim al-Dabari: “He heard Abd al-Razzaq’s works when he was seven years old or thereabouts. Yet he transmitted rejected hadiths from Abd al-Razzaq, and uncertainty arose concerning them: whether they were indeed from him, with al-Dabari alone transmitting them, or whether they were recognized reports among those uniquely transmitted by Abd al-Razzaq.”