There is consensus among the scholars that talbiyah is a prescribed practice. Umm Salamah reported: “I heard Allah’s Messenger (peace be upon him) saying: “O Family of Muhammad! Whoso among you intends to perform Hajj must raise his voice while uttering talbiyah.” This is reported by Ahmad and Ibn Hibban.
The scholars disagree, however, on its legal status, timing, and the position of one who delays it. Ash-Shafi’i and Ahmad hold that it is sunnah of the Prophet (peace be upon him); it is desirable to utter it when putting on the garb of ihram. Thus, if a person intended to perform Hajj but did not utter talbiyah, his Hajj would still be valid, and he is not required to do anything, because according to them, such a person enters the state of ihram just by making intention to perform Hajj.
Hanafi scholars hold that talbiyah or any substitute for it – such as containing praise or glorification of Allah. and bringing an animal for sacrifice – is a requisite condition for the validity of ihram. If someone puts on the garb of ihram without uttering talbiyah or glorifying Allah or bringing a sacrificial animal, his ihram is not valid, because ihram, according to them, is a combination of intention and one of the rites of Hajj. Thus, if one declares his intention for ihram and performs any of the rites of Hajj, for example if he glorifies Allah or declares, “There is no deity worthy of worship but Allah alone,” or if he brought his sacrificial animal along with him but did not utter talbiyah, his ihram will be valid but he will be required to sacrifice an animal as a penalty for failing to do so.
According to the well-known position of Imam Malik, uttering talbiyah is obligatory and in cases where one fails to do so or does not utter it upon donning the garb of ihram but utters it later on, one must slaughter an animal in atonement.