What is the evidence that the sitting for the final tashahhud is a pillar?

The questioner : My brother, I am asking: what is the evidence that the sitting for the final tashahhud is a pillar? It is clear that its name is "sitting."

The Shaykh : What does "other than this" mean? Yes, indeed.

The questioner : Pray as you saw me praying, pray.

The Shaykh : No, this is a completion of Yusuf's statement.

The questioner : Because the sitting is a pillar.

Another questioner : To my colleague: tashahhud and tashahhud, and this is a sitting.

The Shaykh : Yes, correct. The sitting: there is no tashahhud except in a sitting, and the Messenger (peace and blessings be upon him) has no tashahhud except in the sitting. For this reason, we say "the sitting of the obligatory prayer," and the sitting of the obligatory prayer is obligatory. Good. Yes.

The questioner : My uncle, regarding the operation of safety benefits.

The Shaykh : No, no, we do not want the general texts if the specific evidence is available. Yes, Faisal.

The questioner : Shaykh, in Zayd, from the Prophet (peace and blessings be upon him) it becomes morning.

The Shaykh : It is not that; "when one of you sits, let him say" — it is not that, meaning there is no harm in it. In any case, the Messenger (peace and blessings be upon him) does not perform tashahhud except with that. Also, the sitting is attributed to the obligatory prayer, so it must be obligatory. Good.