A.T. Robertson Commentary Acts 10:9

"Now on the morrow, as they were on their journey, and drew nigh unto the city, Peter went up upon the housetop to pray, about the sixth hour:" — Acts 10:9 (ASV)

On the morrow (τη επαυριον). Locative case of article with the compound adverb (ημερα day being understood), the second day after leaving Caesarea, 28 miles from Joppa. The third day (the next morrow, verse 23) they start back home and the fourth day (on the morrow again, verse 24) they reach Caesarea.

As they (εκεινων). The party of three from Caesarea. Genitive absolute with present participle οδοιπορουντων (journeying) and εγγιζοντων (drew nigh).

The housetop (το δωμα). Old word and in Gospels (Luke 3:19, etc.), but only here in Acts. From δεμω, to build, and so any part of the building (hall, dining room, and then roof). The roof was nearly flat with walls around and so was a good place for meditation and prayer and naps.