John Gill Commentary Acts 18:20

"And when they asked him to abide a longer time, he consented not;" — Acts 18:20 (ASV)

When they desired him to tarry longer time with them
Either Aquila and Priscilla, whom he left here, for here they were, as is certain from Acts 18:24,26
or rather the Jews with whom he reasoned, who might be desirous of further conference with him, upon the subject they had disputed about; either in order to gain more knowledge, or in hopes of baffling and confounding him:

he consented not ;
for a reason afterwards given.