The two terms mashhad and mashāhid that occur in this treatise are part of Ibn al-Qayyim’s stock vocabulary in several of his works. (1)

Result
From the various lines of evidence presented above, it becomes clear that attributing the treatise to Ibn al-Qayyim is unquestionably correct—especially since it contains quotations from Ibn Taymiyyah, whom Ibn al-Qayyim is known to cite profusely.

The importance of this treatise
Although brief in size, the work contains pearls from Ibn al-Qayyim that do not appear in any of his printed books (2). It also elaborates on points that he mentioned only in outline elsewhere. This may be seen in the following:
1 – Nowhere in his printed writings does he mention the six mashāhid (contemplative stations) of the prayer that gladden the eye and bring rest to the heart.
2 – In none of his published works does he speak in the manner found here about the verse, “And do not obey the one whose heart We have made heedless of Our remembrance” (al-Kahf 18:28).
3 – When discussing the Almighty’s words in Sūrat al-Fātiḥah, “Guide us to the straight path” (6) and the subsequent verses, he offers valuable reflections on these passages,