And he commanded them to be baptized. It was not of necessity that baptism should be ministered by Peter's hand, as Paul doth likewise testify that he baptized few at Corinth, for other ministers might take this charge upon them. Whereas he saith, in the name of the Lord, it must not be restrained unto the form, as we have said in the third chapter; but because Christ is the proper scope of baptism, therefore are we said to be baptized in his name. When as Luke saith, last of all, that Peter was requested by Cornelius and his kinsmen that he would tarry a few days, he commendeth in them their desire to profit. They were, indeed, endued with the Holy Ghost; but they were not so come to the top, but that confirmation was as yet profitable for them. And, according to their example, so often as opportunity to profit offereth itself, we must use it diligently; and let us not swell with pride, which stoppeth the way before doctrine. [1]

Footnotes

1 - "Qui ingressum obstruat doctrinae," which obstructeth the entrance of doctrine.

And he commanded them - Why Peter did not himself baptize them is unknown. It might be, perhaps, because he chose to make use of the ministry of the brethren who were with him, to prevent the possibility of future cavil. If they did it themselves, they could not so easily be led by the Jews to find fault with it. It may be added, also, that it seems not to have been the practice of the apostles themselves to baptize very extensively. See 1-Corinthians 1:14-17, "Christ sent me not to baptize, but to preach the gospel."

To be baptized in the name of the Lord - That is, in the name of Jesus Christ; which implied their taking upon them the public profession of Christianity, and believing on Christ Jesus as their Savior and Sovereign; for, as they were baptized in his name, they professed thereby to be his disciples and followers.
Then prayed they him to tarry certain days - They felt the necessity of farther instruction, and prayed him to continue his ministry a little longer among them; and to this he no doubt consented. This was properly speaking, the commencement of the Christian Church, as composed of Jews and Gentiles, partaking of the same baptism, united under the same Head, made partakers of the same Spirit, and associated in the same aggregate body. Now was the middle wall of partition broken down, and the Gentiles admitted to the same privileges with the Jews.
1. God is wonderful in all his works, whether they be works of creation, providence, or grace. Every thing proclaims his power, his wisdom, and his goodness. Every where we learn this truth, which is indispensably necessary for all to know who desire to acknowledge God in all their ways that "there is nothing which concerns their present or eternal welfare in which God does not interest himself." We often, to our great spiritual detriment, lose sight of this truth, because we think that the Majesty of God is too great to be occupied with those common occurrences by which we are often much affected, in things which relate, not only to our present, but also to our eternal interests. This is impossible; for God is our father, and, being every where present, he sees our state, and his eye affects his heart.
2. Let the reader examine the chain of Providence (composed indeed of very minute links) brought to light in the conversion of Cornelius, the instruction of Peter, and opening the door of faith to the Gentiles, and he will be convinced that "God has way every where, and that all things serve the purposes of his will." We have already seen how particularly, both by gracious and providential workings, God prepared the mind of Cornelius to receive instruction, and the mind of Peter to give it; so that the receiver and giver were equally ready to be workers together with God. This is a general economy. He who feels his want may rest assured that, even then, God has made the necessary provisions for his supply; and that the very sense of the want is a proof that the provision is already made. Why then should we lose time in deploring wretchedness, for the removal of which God has made the necessary preparations? Mourning over our miseries will never supply the lack of faith in Christ, and very seldom tends even to humble the heart.
3. As the eye of God is ever upon us, he knows our trials as well as our wants; and here, also, he makes the necessary provision for our support. We may be called to suffer, but his grace will be sufficient for us; and, as our troubles increase, so shall the means of our support. And even these trials and temptations will be pressed into our service, for all things work together for good to them that love God, Romans 8:28.
4. We must beware neither to despise outward rites in religion, nor to rest in them. Most people do either the one or the other. God gives us outward helps, because he knows we need them. But do we not sometimes imagine ourselves to be above that which, because of our scantiness of grace, is really above us? We certainly may over-rate ourselves, and under-rate God's bounties. He who is taught by the Spirit of God will be saved from both.

And he commanded them to be baptized,.... By some of the six brethren that came with him from Joppa, who might all of them, at least some of them, be ministers of the Gospel: and this he ordered to be done
in the name of the Lord; that is, of the Lord Jesus Christ, though not to the exclusion of the Father, and of the Spirit: perhaps the phrase, "in the name of the Lord", may stand connected with the word commanded; and the sense be, that in the name of the Lord, and by authority from him, he ordered them to be baptized:
then prayed they him to tarry certain days; partly to express their gratitude to him for the favour they had received through him as an instrument, and partly that they might be more instructed and established by him. And these baptized persons very likely laid the foundation of a Gospel church state in this place, which we find to continue in succeeding ages; in the "second" century Theophilus presided over it; and in the "third" century Origen and Pamphilus, were presbyters of it; and in the same age, succeeding one another, Theoctistus, Domnus, and Theotecnus were bishops of it; and in the beginning of the "fourth" century, Eusebius the famous ecclesiastical historian was bishop of this church, after him Acacius; in the fifth century Gelasius the successor of Eunomius bore the same office in it; and in the "sixth" century the bishop of this place was present in the fifth synod at Constantinople; and in the "seventh" century it appears there was a church in this place: in which century the Arabians, after they had besieged this city seven years, took it, and killed seven thousand persons in it; and since it has been in the hands of the Turks; and this seems to have put an end to the ecclesiastical state of this place, as Christian (s).
(s) Magdeburg. Hist. Eccles. cent. 2. c. 2. p. 2. cent. 3. c. 2. p. 1. c. 7. p. 109. c. 10. p. 153. cent. 4. c. 2. p. 2. cent. 5. c. 2. p. 2. cent. 6. c. 2. p. 3. cent. 7. c. 2. p. 2. c. 3. p. 19.

he commanded them to be baptized--not doing it with his own hands, as neither did Paul, save on rare occasions (1-Corinthians 1:14-17; compare Acts 2:38; John 4:2).
prayed . . . him to tarry certain days--"golden days" [BENGEL], spent, doubtless, in refreshing Christian fellowship, and in imparting and receiving fuller teaching on the several topics of the apostle's discourse.

Commanded them to be baptized. All who heard and upon whom the Holy Spirit fell.
In the name of the Lord. In acknowledgment of his authority. All the baptisms of Acts are in his name, but into the names of the Father, and the Son, and the Holy Spirit.

In the name of the Lord - Which implies the Father who anointed him, and the Spirit with which he was anointed to his office. But as the Gentiles had before believed in God the Father, and could not but now believe in the Holy Ghost, under whose powerful influence they were at this very time, there was the less need of taking notice, that they were baptized into the belief and profession of the sacred Three: though doubtless the apostle administered the ordinances in that very form which Christ himself had prescribed.