What is the ruling on raising the right index finger and pointing it towards the sky when a new Muslim pronounces the Two Testimonies of Faith (Shahadatayn)?

There is no specific evidence reported regarding raising the index finger when uttering the Two Testimonies for someone wishing to embrace Islam. However, some scholars have stated the permissibility and desirability of raising the index finger when uttering the word of monotheism (Tawhid) in general, both inside and outside of prayer. It is called "al-sabbabah" (the index finger) because it is used to point to Tawhid, so that the outward and inward indications of Tawhid may correspond.