Peter asked this so that no one could object to baptizing these Gentiles. The Jewish believers who came with him were astonished. Barnes says they were "amazed that Gentiles should be admitted to the same favor as themselves." Peter's question points to what everyone had just seen. Barnes reasons that God had shown Himself to them as He did to the Jews at Pentecost, so "they are entitled to the privilege of Christian baptism." Gill says converted Gentiles "have as good a right as any to this ordinance." Matthew Henry puts it most sharply: "can we deny the sign to those who have received the thing signified?"

No one objected. Peter "commanded them to be baptized in the name of the Lord," and they asked him to stay "certain days" (Acts 10:48). Later, when believers in Jerusalem contended with him for eating with uncircumcised men, Peter told the whole story and ended with a similar question: "what was I, that I could withstand God?" (Acts 11:2-3, 17). Then "they held their peace, and glorified God, saying, Then hath God also to the Gentiles granted repentance unto life" (Acts 11:18).

The word "forbid" translates the Greek kolysai, from koluo, which Thayer defines as "to hinder, prevent, forbid." The same verb appears when the Ethiopian eunuch asks, "what doth hinder me to be baptized?" (Acts 8:36), and when Peter asks in Jerusalem, "what was I, that I could withstand God?" (Acts 11:17).

Here the Holy Ghost came before water baptism. Matthew Henry notes that the Spirit "fell upon those who were neither circumcised nor baptized." Peter later said the Spirit fell on them "as on us at the beginning" (Acts 11:15), pointing back to Pentecost.

Through this question God made plain that the Gentiles belong in His family on the same footing as Jewish believers. Peter did not decide it by debate. God decided it by pouring out His Spirit, and Peter simply asked who could stand against what God had done. At the Jerusalem council Peter said it again: God gave them the Holy Ghost "even as he did unto us; and put no difference between us and them, purifying their hearts by faith" (Acts 15:8-9).

Gill sums it up: "there is but one baptism for both." The Gentiles' welcome did not come through circumcision or the customs of Israel, but through hearing the word and receiving God's Spirit.