The Sunnah is to look at and focus on the index finger during tashahhud and not to extend the sight beyond the index finger. This view of the Ahlul Hadith is supported by a number of textual evidences.
The First Evidence
Abdullah b. az-Zubayr narrates from his father, az-Zubayr RadhiAllahu Anhuma narrates the Prophet Sallalalhu Alayhi Wasallam
“His sight did not go beyond the pointing (of his index finger) [meaning he focussed on his index finger]” (Abu Dawud (no.990), Sahih Ibn Khuzaymah (no.718), Sahih Ibn Hibban (al-Ihsan) (3/201 no.1941), al-Bayhaqi, Sunan al-Kubra (2/190 no.2790), al-Baghawi, Sharh as-Sunnah (no.677) and its chain is Hasan while its origin is in Sahih Muslim (no.579).
Muhammad b. Ajlan in the chain transmits by An’ana however, in Musnad Ahmad (4/3 no,16145), al-Fath ar-Rabbani (4/115) he clarified he heard the hadith directly. This hadith was graded authentic by Imams Abu Awanah, Ibn Khuzaymah and Ibn Hibban while an-Nawawi and Ibn Mulaqqin graded the chain authentic. (Mustakhraj Abi Awanah (no.2018), Sahih Ibn Khuzaymah (no.718), Sahih Ibn Hibban (al-Ihsan) (no.1941), Khulasah al-Ahkam (1/427), at-Tawdhih (7/32).
Shaykh Shams ul-Haq al-A’zimabadi said,
“That is that his sight follows the pointing (of his finger) since it is the etiquette of conforming to humility. It means he does not look at the sky with signifying Tawhid which is the practise of some people, rather he should look at his finger and not beyond this.” (A’wn al-Ma’bud (3/197)
Shaykh Abdur Rahman al-Mubarakpuri said,
“Benefit: The Sunnah is that a person should not look beyond the pointing of his finger as the aforementioned hadith of Ibn az-Zubayr mentions. It should be pointed towards the Qiblah with the intent of indicating at-Tawhid and sincerity.” (Tuhfatul Ahwadhi (2/160).
Someone might argue this is not the meaning of this hadith, that the Prophet Sallalahu Alayhi Wasallam fixated on his index finger, but it means he did not look beyond his index finger yet his focus could have been on anything closer than his index finger.
Imam Ibn Khuzyamah clarifies this doubt through his chapter title and hence shows this was the view of the early Ahlul Hadith, Imams of Hadith and Sunnah. He adds the chapter, “To Look at the [index] Finger While Pointing with it in Tashahhud.” (Sahih Ibn Khuzaymah (1/355 no.718). Imam al-Bayhaqi wrote the following chapter heading, “The Sunnah is not to Look Beyond the Pointing of the Finger.” (as-Sunan al-Kubra (2/90)
The Second Evidence
“On the authority of Abdullah b. Umar, He saw a man moving pebbles with his hand while praying. When he finished, Abdullah said to him: “Do not move the pebbles since you are praying, for that is from Shaytan. Rather do what the Messenger of Allah Sallalahu Alayhi Wasallam used to do.” He said: “What did he used to do?” He said, “He would put his right hand on his right thigh, and point with the finger next to his thumb [index finger] towards the Qiblah, and he would look at it (the pointing of the finger) or thereabout.” Then he said: “This is what I saw Allah’s Messenger Salallahu Alayi Wasallam doing.” (an-Nasa’i (no’s.1160, 1265, 1266), its chain is authentic and its origin is in Sahih Muslim (no.580), Abu Dawud (no.987), Sahih Ibn Khuzaymah (no.719), Sunan al-Kubra (2/132)
This hadith was graded authentic by Imams Abu Awanah, Ibn Khuzaymah and Ibn Hibban. (Mustakhraj Abi Awanah (no.2017), Sahih Ibn Khuzaymah (no.719), Sahih Ibn Hibban (3/202 no.1944) and Shaykh al-Albani in Sahih Sunan an-Nasa’i.
Imam an-Nasa’i placed in under the following chapter: “Where to look During Tashahhud.” (Sunan an-Nasa’i (no.1160). Imam Abu Awanah Israfayni established the following chapter, “In Clarifying in Pointing with the Finger to the Qiblah and Fixating on it.” (Mustakhraj Abu Awanah (1/539 no.2017).
Shaykh Muhammad Ataullah Hanif al-Bhojiyani said,
“Meaning – he would turn his sight to his finger and Naf’i said when Abdullah b. Umar RadhiAllahu Anhuma would sit in prayer he would place his hands on his knees and point with his finger and fix his sight on it and he then said, Allah’s Messenger Sallalahu Alayhi Wasallam said, “This is more severe on shaytan than an iron rod.” (Ahmad (2/119) as cited in Mishkat.” (at-Ta’liqat as-Salafiyyah A’la Sunan an-Nasa’i (2/178).
Imam an-Nawawi said,
“It is from the Sunnah not to look beyond the pointing of the finger.” (Sharh Sahih Muslim (6/81).
He further said while expanding on the issue of pointing with the finger,
“The fifth: Not to move your sight beyond the pointing of the finger, al-Bayhaqi and others used the hadith of Abdullah b. az-Zubayr as evidence that the Prophet Sallalahu Alayhi Wasallam placed his right hand (on his right knee) and pointed with his finger and his sight did not go beyond it. And Abu Dawud transmitted it with an authentic chain and Allah knows best.” (al-Majmu’ Sharh al-Muhazzab (3/302).
Hafiz Ibn Rajab said,
“Our Companions said it is recommended when a person sits for tashahhud not to look beyond the pointing of the finger.” (Ibn Rajab, Fath ul-Bari (6/369).
Shaykh Abdul Aziz b. Baz said,
“The Sunnah when sitting (in prayer) is to look at the pointing of the finger when sitting for tashahhud or between the two sujud.” (Ibn Baz, Majmu’ Fatawa (29/241).
Shaykh Muhammad b. Salih al-Uthaymin said something similar.
While some madhhabs advocate looking at ones lap or the area between the thighs!!! And according to another opinion, to generally look at the lap and only at the index finger when indicating with it. The Sunnah and hadith of Allah’s Messenger Sallalahu Alayhi Wasallam takes precedence over all other opinions.