Albert Barnes Commentary Acts 25:3

"asking a favor against him, that he would send for him to Jerusalem; laying a plot to kill him on the way." — Acts 25:3 (ASV)

And desired favour against him. They desired the favour of Festus so that they could accomplish their wicked purpose against Paul.

Would send for him to Jerusalem. This request was probably made under the pretense that he might be tried by the Sanhedrin, or perhaps they wished Festus to hear the case there and decide it while he was at Jerusalem. Their real motive is immediately stated.

Laying wait in the way to kill him. That is, they intended to lie in wait, or they would employ a band of Sicarii, or assassins, to take his life on the journey. See Barnes on Acts 21:38; see also Barnes on Acts 23:12.

It is altogether probable that if this request had been granted, Paul would have been killed. But God had promised him that he would bear witness to the truth at Rome (Acts 23:11); and His providence was remarkable in thus influencing the mind of the Roman governor and defeating the plans of the Jewish council.