Albert Barnes Commentary Acts 18:5

"But when Silas and Timothy came down from Macedonia, Paul was constrained by the word, testifying to the Jews that Jesus was the Christ." — Acts 18:5 (ASV)

And when Silas and Timothy, etc. They came to Paul according to his request, which he had sent by the brothers who accompanied him from Thessalonica (Acts 17:16).

Paul was pressed. He was urged; he was borne away by an unusual impulse. It was deeply impressed on him as his duty.

In spirit. In his mind, in his feelings. His love for Christ was so great, and his conviction of the truth so strong, that he laboured to make known to them the truth that Jesus was the Messiah.

That Jesus was Christ. That is, Jesus of Nazareth was the Messiah. . The presence of Silas and Timothy animated him, and the certainty of aid in his work urged him to zeal in making known the Saviour.