Some interpreters today suggest that the apostles made a mistake in casting lots for a twelfth apostle, even though it was before the day of Pentecost. The immediate context, however, suggests something positive; the believers were in prayerful unity (1:12-14; 2:1), and now Peter has exhorted them to replace the lost apostle (1:15-26). Would Luke spend so much space to describe a practice he disagreed with, and then fail to offer any word of correction?
Whole-book context in Acts actually invites us to read Luke and Acts together, for they were two volumes of one work (Acts 1:1-2; cf. Lk 1:1-4). When we read them together we see that Luke’s Gospel also opens with a casting of lots, in this case, one used to select which priest would serve in the temple (Lk 1:9). In that case, God certainly controlled the lot, for by it Zechariah was chosen to serve in the temple, and subsequently received a divine promise specifically designed for himself and Elizabeth, the promise of a son, John the Baptist (1:13). If God controlled the lot in the opening story of volume one, why not in the opening story (after repeating the ascension) in volume 2? The background would help us further: if God controlled the lot throughout the Old Testament, including for selection of levitical ministries, why should we doubt that he used this method on this one occasion in Acts, before the Spirit’s special guidance inaugurated with Pentecost (2:17).