Acts 2:42

We often speak of the primitive church, and appeal to it, and to the history of it; in these verses we have the history of the truly primitive church, of the first days of it, its state of infancy indeed, but, like that, the state of its greatest innocence. I. They kept close to holy ordinances, and abounded in all instances of piety and devotion, for Christianity, admitted in the power of it, will dispose the soul to communion with God in all those ways wherein he has appointed us to meet him and promised to meet us. 1. They were diligent and constant inn their attendance upon the preaching of the word. They continued in the apostles' doctrine, and never disowned nor deserted it; or, as it may be read, they continued constant to the apostles' teaching or instruction; by baptism they were discipled to be taught, and they were willing to be taught. Note, Those who have given up their names to Christ must make conscience of hearing his word; for thereby we give honour to him, and build up ourselves in our most holy faith. 2. They kept up the communion of saints. They continued in fellowship (Act 2:42), and continued daily with one accord in the temple, Act 2:46. They not only had a mutual affection to each other, but a great deal of mutual conversation with each other; they were much together.

— Matthew Henry's Concise Commentary (public domain)

continued steadfastly in--"attended constantly upon." the apostles' doctrine--"teaching"; giving themselves up to the instructions which, in their raw state, would be indispensable to the consolidation of the immense multitude suddenly admitted to visible discipleship. fellowship--in its largest sense. breaking of bread--not certainly in the Lord's Supper alone, but rather in frugal repasts taken together, with which the Lord's Supper was probably conjoined until abuses and persecution led to the discontinuance of the common meal. prayers--probably, stated seasons of it.

— Jamieson-Fausset-Brown Commentary (public domain)