Because your heart is not right before God

Acts 8:1-40
On that day a great persecution broke out against the church in Jerusalem, and all except the apostles were scattered throughout Judea and Samaria.
But Saul began to destroy the church. Going from house to house, he dragged off both men and women and put them in prison.
Peter answered to Simon : “May your money perish with you, because you thought you could buy the gift of God with money! You have no part or share in this ministry, because your heart is not right before God.
Now an angel of the Lord said to Philip, “Go south to the road—the desert road—that goes down from Jerusalem to Gaza.” So he started out, and on his way he met an Ethiopian eunuch, an important official in charge of all the treasury of the Kandake.
And he gave orders to stop the chariot. Then both Philip and the eunuch went down into the water and Philip baptized him. When they came up out of the water, the Spirit of the Lord suddenly took Philip away, and the eunuch did not see him again, but went on his way rejoicing. Philip, however, appeared at Azotus and traveled about, preaching the gospel in all the towns until he reached Caesarea.
The persecution that follows Stephen;s death leads to the first broadening of the church's outreach. The attack seems to have concentrated on Stephen's fellow Hellenists, leaving the apostles free to remain in Jerusalem.
Wherever the scattered believers went they took the message with then - in Philip's case with such marked success that two of the apostles come down to see what is happening. It is Philip's power which draws Simon, and he covets the power to convey the gift of the Spirit, needing Peter's stern words to set him right.
At the height of Philip's flourishing Samaritan campaign God calls him away to meet the need of an individual. Eunuchs were barred from the Temple, but God knows this foreigner is ready to receive the Good News about Jesus.
Why?
Persecution came seems worse to Christians but it is the way of the Lord let Gospel could be preaching to other places. For the Holy Spirit was with them so Philip may did many wonder and healed the sick.
Simon was attracted by the power of Holy Spirit, but it is the will of the Lord, it could not be purchased so Peter said to Simon," May your money perish with you." because your heart is not right before God.
How?
Right heart is most important to be a Jesus follower.