Who, when they were come down, prayed for them, that they might receive the {d} Holy Ghost:

(d) Those excellent gifts which are necessary, especially for those that were to be appointed rulers and governors of the Church.

People's New Testament

8:15,16 Prayed for them. That the Holy Spirit might fall on them. They had been born of water and the Spirit (Joh 3:5), but had not received that baptism of the Spirit, which conferred miraculous powers. This was bestowed by apostolic prayer and the laying on of hands. I suppose, not on all, but on those selected for teachers and preachers among the Samaritans. Plumptree states:

The prayer clearly pointed to such a power of the Holy Spirit as had been bestowed on Pentecost.''

And Calvin writes:

Luke speaks not of the common grace of the Holy Spirit, but of the singular gifts with which God would have certain endowed at the beginning of the gospel.''

Wesley's Notes

8:15 The Holy Ghost - In his miraculous gifts? Or his sanctifying graces? Probably in both.

Jamieson-Fausset-Brown Bible Commentary

15, 16. prayed . they might receive the Holy Ghost. (For only they were baptized in the name of the Lord Jesus)-As the baptism of adults presupposed "the renewing of the Holy Ghost" (Tit 3:5-7; 1Co 12:13), of which the profession of faith had to be taken for evidence, this communication of the Holy Ghost by the laying on of the apostles' hands was clearly a superadded thing; and as it was only occasional, so it was invariably attended with miraculous manifestations (see Ac 10:44, where it followed Peter's preaching; and Ac 19:1-7, where, as here, it followed the laying on of hands). In the present case an important object was served by it-"the sudden appearance of a body of baptized disciples in Samaria, by the agency of one who was not an apostle, requiring the presence and power of apostles to perform their special part as the divinely appointed founders of the Church" [Alford]. Beautiful, too, was the spectacle exhibited of Jew and Samaritan, one in Christ.

Matthew Henry's Concise Commentary

8:14-25 The Holy Ghost was as yet fallen upon none of these coverts, in the extraordinary powers conveyed by the descent of the Spirit upon the day of Pentecost. We may take encouragement from this example, in praying to God to give the renewing graces of the Holy Ghost to all for whose spiritual welfare we are concerned; for that includes all blessings. No man can give the Holy Spirit by the laying on of his hands; but we should use our best endeavours to instruct those for whom we pray. Simon Magus was ambitious to have the honour of an apostle, but cared not at all to have the spirit and disposition of a Christian. He was more desirous to gain honour to himself, than to do good to others. Peter shows him his crime. He esteemed the wealth of this world, as if it would answer for things relating to the other life, and would purchase the pardon of sin, the gift of the Holy Ghost, and eternal life. This was such a condemning error as could by no means consist with a state of grace. Our hearts are what they are in the sight of God, who cannot be deceived. And if they are not right in his sight, our religion is vain, and will stand us in no stead. A proud and covetous heart cannot be right with God. It is possible for a man to continue under the power of sin, yet to put on a form of godliness. When tempted with money to do evil, see what a perishing thing money is, and scorn it. Think not that Christianity is a trade to live by in this world. There is much wickedness in the thought of the heart, its false notions, and corrupt affections, and wicked projects, which must be repented of, or we are undone. But it shall be forgiven, upon our repentance. The doubt here is of the sincerity of Simon's repentance, not of his pardon, if his repentance was sincere. Grant us, Lord, another sort of faith than that which made Simon wonder only, and did not sanctify his heart. May we abhor all thoughts of making religion serve the purposes of pride or ambition. And keep us from that subtle poison of spiritual pride, which seeks glory to itself even from humility. May we seek only the honour which cometh from God.