We read in the Silsilah that Al-Albaani said that as far as he knows Ibn Al-Qayyim was the first to hold the legality of pointing between prostrations. Is it true that pointing at this time was never reported from any of the Salaf? Also, is Abdur-Razzaq As-San'ani considered weak when narrating alone from Ath-Thawri?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger. 

The statement of Shaykh Al-Albaani that Ibn Al-Qayyim was the first to hold that view is incorrect. The Maaliki scholar Al-ʻAdawi stated in his book Haashiyat Al-ʻAdawi ʻala Kifaayat At-Taalib Ar-Rabbaani that the apparent indication of the statements of Al-Qaadhi ʻAbd Al-Wahhaab and Ibn Al-Jallaab is that pointing with the index finger applies to both sittings (of the Tashahhud as well as between the two prostrations). Thus, this view was stated by some Maaliki scholars. This clearly answers your first question. Ibn Al-Qayyim was not the first to hold the legality of pointing between prostrations. In fact, this was a matter open for ijtihaad (scholarly reasoning and discretion).

As for the second question, some scholars held that when ʻAbd Ar-Razzaaq is the only reporter narrating a report which contradicts another report narrated on the authority of a more trustworthy reporter or more narrators, then the authenticity of such a report is undermined. Others held otherwise. Hence, scholars maintained different views regarding the authenticity of the report in reference. We believe that the most correct view in this regard is the view suggesting the classification of such a report as weak. This is the position of many great hadeeth scholars such as Sheikh Ibn Baaz and Sheikh Al-Albaani. However, Al-Arnaa’oot, who reviewed Zaad Al-Maʻaad, declared the report authentic based on the view suggesting that ʻAbd Ar-Razzaaq was a trustworthy narrator and that his addition is accepted by hadeeth scholars.

In any case, this is a matter of ijtihaad, as we mentioned. Among the scholars who studied the matter in reference and reached the conclusion that the correct view is that it is not legislated to point between prostrations is the well-versed scholar Bakr Abu Zayd in his treatise “La Jadeed fi Ahkaam As-Salah”. On the other hand, among the scholars who held the legality of pointing between prostrations is the well-versed scholar Ibn ʻUthaymeen, as seen in his book Ash-Sharh Al-Mumti’.

For more benefit, please refer to fatwa 312982.

Allaah knows best.