Many state that Yah (found in Exodus, Psalm and Isaiah) is a short of YHWH. I myself use to say it as well. But where in scripture do we see any names shortened? If we shorten Matthew aka Matti-Yahu to Matt, what have we done? We removed YHWH’s name from the name.
In turn due to studies, that Yah, like god and lord, is an item of the lying pen of the scribes. As YHWH tells us His name many times and that it is forever and for all generations. Not to mention He does not change nor are we to be given to change.
Altering YHWH to Yah falls under commandment 3 of not taking His name in vain (H7723, root is H7722, defining as ruin, destruction, worthlessness, devastation, ravage). The deceiver is tricky and tries his best to get us to fail the commandments at every turn.
And Elohim said moreover unto Moses,
Thus shalt thou say unto the children of Israel,
YHWH (H1961) Elohim of your fathers,
the Elohim of Abraham,
the Elohim of Isaac,
and the Elohim of Jacob,
hath sent me unto you:
this is my name for ever,
and this is my memorial unto all generations.
Thy name, O YHWH (H1961),
endureth for ever;
and thy memorial, O YHWH,
throughout all generations.
I am YHWH (H1961): that is my name:
and my glory will I not give to another,
neither my praise to graven images.
For I am YHWH (H1961), I change not;
therefore ye sons of Jacob are not consumed.