‘So he called them in and lodged them. And on the morrow he arose and went forth with them, and certain of the brethren from Joppa accompanied him.'
So Peter, still puzzling over his vision, and thinking that the two strange events may be connected, said that he would accompany them, meanwhile offering them hospitality for the night. There was no difficulty in this except to the most strict of Jews, especially in a tanner's house. The niceties would still be observed, along with Jewish scruples. And accordingly next day he did accompany them, taking with him a number of Jewish Christians from Joppa (six in all - Acts 11:12 - making with himself the perfect number seven and hopefully sufficient if the three men intended mischief to combat it).
The taking of six fellow-Christians may have been because he felt that their support in prayer might be helpful, or because he was a little apprehensive about going to see a Roman centurion alone in case he was arrested and disappeared without trace. (If a Roman centurion from the provincial capital called for you to go and see him it was usually a good idea to do so, but it could also carry unpleasant consequences). Or he may have felt that they might be known to the centurion, or at least be looked on as ‘locals', and might thus make the visit easier. After all Cornelius was supposed to be known to the Jews of the area. Or he may already have in mind that he might need witnesses to combat any false rumours. The witness of seven men would be indisputable. He had no doubt learned from past experience that witnesses could be valuable when something controversial was happening. Indeed he may have had a mixture of such reasons.