For they heard them speak with tongues, and magnify God. Then answered Peter,

Jamieson-Fausset-Brown Bible Commentary

46. heard them speak with tongues and magnify God-As on the day of Pentecost it was no empty miracle, no mere speaking of foreign languages, but utterance of "the wonderful works of God" in tongues to them unknown (Ac 2:11), so here; but more remarkable in this case, as the speakers were perhaps less familiar with the Old Testament songs of praise.

46-48. Then answered Peter, Can any man forbid water . which have received the Holy Ghost, &c.-Mark, he does not say, They have received the Spirit, what need have they for water? but, Having the living discipleship imparted to them and visibly stamped upon them, what objection can there be to admitting them, by the seal of baptism, into the full fellowship of the Church?

Matthew Henry's Concise Commentary

10:44-48 The Holy Ghost fell upon others after they were baptized, to confirm them in the faith; but upon these Gentiles before they were baptized, to show that God does not confine himself to outward signs. The Holy Ghost fell upon those who were neither circumcised nor baptized; it is the Spirit that quickeneth, the flesh profiteth nothing. They magnified God, and spake of Christ and the benefits of redemption. Whatever gift we are endued with, we ought to honour God with it. The believing Jews who were present, were astonished that the gift of the Holy Ghost was poured out upon the Gentiles also. By mistaken notions of things, we make difficult for ourselves as to the methods of Divine providence and grace. As they were undeniably baptized with the Holy Ghost, Peter concluded they were not to be refused the baptism of water, and the ordinance was administered. The argument is conclusive; can we deny the sign to those who have received the things signified? Those who have some acquaintance with Christ, cannot but desire more. Even those who have received the Holy Ghost, must see their need of daily learning more of the truth.