How sound is Al-Bayhaqi's hadith regarding restricting the movement of the index finger to the times of negation and affirmation when saying "La ilaha illa Allah" (There is no god but Allah), and did the Four Madhhabs use it as a proof?

The restriction of the index finger's movement to the time of negation (Nafy) and affirmation (Ithbat) was not found in Sunan al-Bayhaqi. Rather, the narrated hadith is from Wa'il ibn Hujr concerning the description of the Prophet's prayer (peace be upon him). The Malikis recommend pointing from the beginning of the tashahhud until its end, which is also an opinion among the Shafi'is, but Al-Nawawi weakened it and stated that the correct view is to point at the saying of "illallah" (except Allah). The Hanbalis hold that one should point repeatedly at the word of Majesty "Allah" to emphasize monotheism, but without moving it. As for the Hanafis, there are two opinions: one is not to point at all, and the other is to raise the index finger at the point of negation and lower it at the point of affirmation. All four imams based their opinions on the hadith of Wa'il ibn Hujr.