Acts 8
14 Now when the †apostles who were at Jerusalem heard that Samaria had received the word of God, they sent Peter and John to them,
15 who, when they had come down, prayed for them †that they might receive the Holy Spirit.
Nelson, Thomas. Holy Bible, New King James Version (NKJV) (p. 1066). Thomas Nelson. Kindle Edition.
Acts 19
1 And it happened, while †Apollos was at Corinth, that Paul, having passed through †the upper regions, came to Ephesus. And finding some disciples
2 he said to them, “Did you receive the Holy Spirit when you believed?” So they said to him, †“We have not so much as heard whether there is a Holy Spirit.”
3 And he said to them, “Into what then were you baptized?” So they said, †“Into John’s baptism.”
4 Then Paul said, †“John indeed baptized with a baptism of repentance, saying to the people that they should believe on Him who would come after him, that is, on Christ Jesus.”
5 When they heard this, they were baptized †in the name of the Lord Jesus.
6 And when Paul had †laid hands on them, the Holy Spirit came upon them, and †they spoke with tongues and prophesied.
Nelson, Thomas. Holy Bible, New King James Version (NKJV) (p. 1079). Thomas Nelson. Kindle Edition.
As I said, it is not automatic. And sometimes the Spirit come first and baptism comes later:
Acts 10
44 While Peter was still speaking these words, †the Holy Spirit fell upon all those who heard the word.
45 †And those of the circumcision who believed were astonished, as many as came with Peter, †because the gift of the Holy Spirit had been poured out on the Gentiles also.
46 For they heard them speak with tongues and magnify God. Then Peter answered,
47 “Can anyone forbid water, that these should not be baptized who have received the Holy Spirit †just as we have?”
48 †And he commanded them to be baptized †in the name of the Lord. Then they asked him to stay a few days.
Nelson, Thomas. Holy Bible, New King James Version (NKJV) (pp. 1069-1070). Thomas Nelson. Kindle Edition.
The Simon who wanted to buy the power to confer the holy Ghost (which no Apostle or any other human has ever possessed) was a "believer" but unsaved, whether baptized or not (water baptizing does not and cannot save).
The "believers" encountered by Paul in Ephesus were not hearers or believers of the saving Gospel (though accounted as disciples of Scripture teachers). Paul recruited, enlisted, and inducted them by baptism into the discipleship of Jesus' ordained teacher(s); they then each believed redemptively, and were graced in an unusual and glorious way by the Holy Ghost, pursuant to their exercise of a saving faith.
SM also says: As I said, it is not automatic.
No, there is nothing automatic about the gift of the Indwellingness of The Holy Ghost. It is entirely of the Will of The Father, through the agency of The Spirit (1 Cor. 12:13), and it only occurs when He knows that the receiver has yielded him/herself to a joint commitment which will never be abandoned (Hebrews 13:6). How can God know that? Because He has foreknowledge.
Regarding water baptism (there are six other baptisms in the NT, not counting ritual cleansing in the mikvah for Temple worship and service); it is administered by fallible men for the purpose of signifying a believer's commitment; and is carried out as the public ritual of induction into the temporal process of sanctification of the new recruit. By it he comes under the authority and ownership of the Father, of The Son, and of The Holy Ghost. Human-administered water baptism does not confer God's retraction of punishment for sins. Only one's complete faith in the substitutionary punishment and death of God's Beloved Incarnate Son can cause the transaction of suffering of The Lamb of God for ones sins, and the imputation of The Lamb's innocence to the believer, to occur. With it, The Father, reconciled by the Redeemer's blood price for ownership of the yielded believer(s), judicially frees the supplicant from guilt, and can then offer intimate fellowship to the saved one(s). With that verdict He confers gift of the indwelling Holy Spirit as the true, earnest, internal, eternal seal of the permanence of that exchange.
That probably sounds a little complicated, but think it through, and you'll get it.
On the other matter regarding parable of the sower and the seed (Mt. 13:3-9), Jesus told it to demonstrate to his disciples that those who could or would not understand it were not saved (v. 15), and did not have spiritual discernment. In any case, He says that the "seed" represents the Word(s) of the Kingdom (v. 19). It does not represent The Holy Ghost, who is of the same substance of, inseparable from, and never absent from the Father and The Son. So including the terms of that parable in your statement to which I responded was a little odd, a non sequitur, I thought.