‘But Saul, who is also called Paul, filled with the Holy Spirit, fastened his eyes on him, and said, “O full of all guile and all villainy, you son of the devil, you enemy of all righteousness, will you not cease to pervert the right ways of the Lord?” '
Saul, who was already permanently filled with the Holy Spirit (see comments on Acts 9:17) now received a further temporary though powerful filling for the purpose of his curse. It was thus the Holy Spirit who caused him to say, “O full of all guile and all villainy, you son of the devil, you enemy of all righteousness.” This was not the way in which Saul usually treated genuine opponents. Through the Holy Spirit he recognised the deliberate deceit and guile, and even worse, that Elymas was using. Furthermore his description of Elymas as ‘you son of the Devil' stresses the evil power that he saw at work in him. Saul saw in what he was saying and doing, not a fair argument but a use of devilish powers to combat the truth. Here was evidence of Satan's working so as to insidiously turn the honest pro-consul against them and possibly even to keep him from Christ. This is further confirmed by his description of Elymas as an ‘enemy of all righteousness'.
‘You son of the Devil.' Luke wants us to see from the commencement of this journey among Gentiles that any powers they could rely on were as nothing before the Lord. The Devil may oppose, but God would be triumphant.
He then accused him of ‘perverting the right ways of the Lord'. Saul was very conscious that humanly speaking a man's soul might be at stake, or even their own right to be able to speak on the island. And this evil man, possessed by Satan, was using all foul means that he could to prevent either the one or the other. It is a clear indication of his opinion of the man's deliberate deceitfulness.
‘Saul, who is also called Paul.' Saul was his Hebrew name, Paul his Greek name. He would also have had a Roman name, but we do not know what it was. Now that his ministry is to be mainly to Greek speakers Luke will use his Greek name.