I wanted to know that is it true that when reciting the letters you need to say from the articulation point without moving the jaw.

Question
Assalamu alaikum
i wanted to know that is it true that when reciting the letters you need to say from the articulation point without moving the jaw. For instance the letter ta -tip of the tongue touches the top of the gum, when the tongue touches the top part the mouth has be (very) still.

i heard this from someone else and i believe it will be difficult for people to pronounce the letters without some movement.
please can you let know regarding this issue.

Answer
When we pronounce letters, there are either no mouth or jaw movements, such in a saakin letter, or there are mouth or jaw movements, such in a voweled letter.
If the letter  is saakinah (no vowel), then we use the top of the tip of the tongue and hit it to the area where the roots of the teeth lie (slightly higher up than the gum) and there should be no mouth or jaw movement.  If however the has a fathah on it, we must open our mouth vertically for the fathah sound to come out.  If the has a dhammah, we must make a circle of our lips like we do with the wow to get the correct dhammah sound, and if it has a kasrah, we must lower our jaw, meaning as we do when we smile with our teeth showing. 
Please see the following two lessons for more clarification:
http://www.abouttajweed.com/the-mechanism-for-the-formation-of-letters/the-mechanism-of-the-formation-of-letters-part.html
http://www.abouttajweed.com/the-mechanism-for-the-formation-of-letters/the-mechanism-of-the-formation-of-letters-pa.html

It is therefore only the saakin letters (not including the medd letters) which have no accompanying mouth and jaw movements, just as in English when we have a letter with no vowel after it (like the M in number), we do not add one or it changes the word and meaning.