John Gill Commentary Acts 9:7

"And the men that journeyed with him stood speechless, hearing the voice, but beholding no man." — Acts 9:7 (ASV)

And the men who journeyed with him
Out of respect to him, to keep him company; or rather to assist him in his designs:

stood speechless :
astonished and amazed, they did not have power to speak one word, nor to rise from the ground, and move one step forward; they were as if they were thunderstruck, and fastened to the earth; for this standing is not opposed to their being fallen to the earth, but to their going forward, and only expresses the surprise and stupidity that had seized them:

hearing a voice, but seeing no man ;
that is, they heard the voice of Saul, saying, who are you? and what will you have me to do? but saw nobody that he spoke to, which surprised them; for it is certain they did not hear the voice of Christ, that spoke to him, (Acts 22:9) or if they heard the voice of Christ, it was only the sound of his voice, but did not understand what he said; but the former seems rather to be the sense, and the best way of reconciling the two passages.