Shaykh al-‘Uthaymīn (d. 1421AH):
The place of al-niyyah is the heart, and it has no place upon the tongue in all acts of worship. Hence, the one who verbally utters the niyyah when he intends to pray, observe the fast, perform the Ḥajj, the ablution, or other deeds, is deemed an innovator, and he is declaring in the religion of Allāh that which is not from it.
Translation taken from: TROID.ORG
