All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Muhammad and upon all of his family and companions.
Person's intention lies in the heart; thus, whosoever intended to perform a devotional act such as: making ablution, paying Zakah, fasting, performing prayer or Hajj is obliged to make his intention in the heart before performing any of which in order to be a valid one, for Allah, The Exalted said (What means):" And they are ordered naught else than to serve Allah, keeping religion pure for Him, as men by nature upright, and to establish worship and to pay the poor-due. That is true religion." [Al-Bayyinah/5].
In this regard, Al-Imam Al-Qutoobi stated in his book [Tafseer Al-Qutroobi vol. 20 pp.144] while interpreting the above verse what follows:" Keeping religion pure for Him: is meant for acts of devotion since Allah, The Exalted said (What means):" Say (O Muhammad): Lo! I am commanded to worship Allah, making religion pure for Him (only). This is an evidence that making one's intention while performing acts of devotion is obligatory because sincerity is combined to the heart only and by which the sake of Allah only is intended but none else."
Further, Al-Imam Al-Bukhary (may Allah have mercy on his soul) stated in his Sahih that Alkama Ibn Wqaas Al-Laithy reported:" I heard Allah's Messenger (PBUH) saying, "The reward of deeds depends upon the intentions and every person will get the reward according to what he has intended. So whoever emigrated for worldly benefits or for a woman to marry, his emigration was for what he emigrated for.".
As for uttering one's intention at the performance of the above acts, the majority of Muslims' scholars from Hanafiee, Shafiee' and Hanbaliees' doctrine are of the view that uttering one's intention is recommended so that the tongue is working as a reminder for the heart; therefore, making person's intention in this case comes out from a genuine evoking. Besides, it is stated :" Making person's intention in general at the performance of devotional acts is obligatory according to the consensus of Muslims' scholars; thusly, uttering it without being affiliated with the heart won't suffice and this is to be applied at the performance of any act of devotion. Yet, if a person uttered the intention to perform an a devotional act contrary to the one in the heart .i.e. The intention in the heart is to perform the Duher prayer while he uttered it to perform the Asr prayer forgetfully; therefore, a person is recommended to utter his intention to a prayer before the opening Takbeer and combine with his heart as well, so that the tongue will help the latter in preparing one's intention in order to ensure prayer's validity and by which the whispers of the devil are no longer effective."
The following narration is an evidence that the utterance of one's intention at the performance of Hajj through Talbiya (Devotional calls while offering Hajj and Umrah) is recommended, it states:" "Anas said: 'I heard the Prophet reciting the Talbiyah for 'Umrah and Hajj together. I told Ibn 'Umar about that and he said: "He recited the Talbiyah for Hajj only. I met Anas and told him what Ibn 'Umar had said, and Anas said: "do you think of us as no more than children? I heard the Messenger of Allah say: 'Labbaika 'Umratan wa Hajjan ma'an (Here I am (O allah) for 'Umrah and Hajj together). [Related by Al-Bukhary].
As a result, some scholars adopted Qiyas (Deduction by analogy) in uttering the intention while performing ablution and prayers based on what been mentioned in the above narration at the performance of Hajj; in this regard, Ibn Hajar Al-Haythami commented on Al-Nawawi saying " Its recommended to utter one's intention at the performance of devotional acts before being initiated with the opening Takbir." :" so that the tongue will help the heart in preparing and combining one's intention as well as to avoid disagreement and opposite opinions from other parties by using Qiyas on what is mentioned on the uttering the intention at the performance of Hajj." [Tohfat Al-Muhtaj Alaa' Sharih Al-Minhaj vol.2/pp.12]. For further details in this regard, kindly refer to [Al-Durr Al-Mukhtar Wa Hashyat Ibn Abdeen vol.1 pp.127] and [Khshaf Al-Qinaa' A'n Matin Al-Iqnaa' vol.1 pp.87].
As for the claim that the utterance of one's intention is an innovation on the basis that neither the Prophet (PBUH) nor the righteous companions did so, this statement contains a great risk because it involves big accusation of Muslim scholars and Muslims misguidance in general; in addition, issuing a religious opinion in order to label someone as a misguided in a juristic sub-matter is impermissible since the majority of Muslim scholars stated that uttering one's intention before performing an act of devotion is permissible. Kindly refer to [Merkhat Al-Mafateeh Sharih Mishkat Al-Masabeeh vol.1 pp. 42]. And Allah knows best.