Old Arabic

There are thousands of those inscriptions written here's a database of it http://krc.orient.ox.ac.uk/ociana/index.php/database

Safaitic exists in a dialect continuum with Classical Arabic and some of its interesting (non-classical) features survive in modern Levantine Arabic:

Qaf ق becoming a glottal stop ء

Ẓa ظ becoming Ḍad ض

The pronunciation of the final ā in ى and ـه sound as ē.

Now while these features might have independently redeveloped in modern Levantine, to me it takes fewer steps to rationalize that these features attested in Safaitic between 2nd century BCE and 4th century CE in the Levant just continued into modern Levantine.