“All these with one accord were devoting themselves to prayer, together with the women and Mary the mother of Jesus, and his brothers.” (Acts 1:14)
After the ascension the Apostles realized that they were a new community of faith. They really did not know at this point how to carry out the Lord’s command to spread the gospel and baptize all nations in the name of Jesus. But they stayed together in fellowship and prayer which became the most important task of this fledgling community. In prayer they realized that as a new community, the new Israel, they needed to have 12 apostles, or 12 leaders to represent the original 12 tribes, the 12 patriarchs. Their community had been fractured by the betrayal and suicide of Judas and had to be restored to its fullness. The choice was made by casting lots so that the Lord would be the one who chose the one man He desired to represent Him on earth.
Today if we want to discern the Lord’s will we do not resort to casting lots, throwing dice, or any such random means. We should realize that the apostles consulted the Holy Spirit to discern the will of the Lord in those few days before they received the divine infilling. When we are faced with decisions we too must consult the Holy Spirit who indwells the Church as well as the Christian heart. We do so through prayer, reading the Scriptures, and waiting on the Lord until He reveals clearly to us what we must do. This He will do by means of His Word, our own reasoning, other people or by circumstances.