If someone were to object: The first tashahhud presents a difficulty, for it is a tashahhud, yet the Prophet, peace and blessings be upon him, omitted it and compensated for it with the prostrations for forgetfulness. This is the ruling concerning obligatory duties; so should not the final tashahhud be the same?
The answer is: No. The basic principle is that both tashahhuds are obligatory. The first tashahhud is excepted by the sunnah, since the Messenger, peace and blessings be upon him, compensated for its omission with the prostrations for forgetfulness. Thus, the final tashahhud remains obligatory as a pillar.
And sitting for it, invoking blessings upon the Prophet, peace and blessings be upon him, during it, maintaining the prescribed sequence, and the final salutation.
His statement, “And sitting for it”: this is the eleventh pillar of the prayer—that is, sitting for the final tashahhud is a pillar. If, for example, a person were to rise directly from prostration to a standing position and recite the tashahhud, it would not suffice him, because he has omitted a pillar, namely sitting. He must sit, and the tashahhud must likewise be recited while sitting, as indicated by his statement, “And sitting for it.” He connected the sitting to the tashahhud in order to make clear that the tashahhud must be performed in that very sitting.
His statement, “And invoking blessings upon the Prophet, peace and blessings be upon him, during it”: that is, during the final tashahhud. This is the twelfth pillar of the prayer.
The evidence for this is that the Companions, may Allah be pleased with them, asked the Prophet, peace and blessings be upon him: “O Messenger of Allah, teach us how to greet you with peace; how, then, should we invoke blessings upon you?” He said: “Say: O Allah, send blessings upon Muhammad and upon the family of Muhammad.” (1) The command denotes obligation, and the basic ruling regarding an obligation is that it is mandatory: if it is omitted, the act of worship is invalid. This is how the jurists, may Allah have mercy on them, have formulated the proof for this issue. (2)