The two phrases are not used interchangeably. The first phrase, ἐπίστευσαν εἰς αὐτόν (believed in Him), is recognized as the “stronger” faith statement:
Then said Jesus to those Jews which believed on him. Better, Jesus said, therefore, to the Jews who had believed Him. There is a change in the expression respecting their belief. In John 8:30 S. John uses the strong phrase ‘believed on Him;’ here he uses the much weaker ‘believed Him’ (see on John 1:12), as if to prepare us for the collapse of their faith. [John 8:31 Cambridge Bible for School and Colleges Commentary]
As discussed in more detail in my answer to the question In John 8:31–44, does Jesus refer to “the Jews who believed in him” as children of the devil? “believe in…” is used 33 times in John and 2 times in 1 John. These 35 uses make up almost 80% of those in the New Testament. On the other hand, the phrase “believed Him” is nowhere else used in the Gospel.1 “Believe in…” is the fundamental statement of belief in the Johannine corpus.
The verse cited in the Cambridge commentary focuses attention on the key aspect of belief the writer of the Fourth Gospel is attempting to make:
But as many as received Him, to them He gave the right to become children of God, to those who believe in His name (John 1:12) [ESV throughout]
Like the passage in 8:30-31, there are two groups of people. The first consists of those who did receive Him. This group has been closed because Jesus returned to His Father and people are no longer able to receive Him as John and others did. The second group, those who believe in His name (πιστεύουσιν εἰς...), remains open unto the present. Also, despite their personal contact with Jesus, those who received Him have the same status as those who believe in His name. Each had/have the ability to become children of God. Like the laborers in the parable of the vineyard (Matthew 20:1-16) the Gospel of John describes an egalitarian family where regardless of how and/or when one comes into the family all are equally "children" of God.
The Gospel ends with an appeal on the same note:
but these are written so that you may believe that Jesus is the Christ, the Son of God, and that by believing you may have life in his name. (John 20:31)
The purpose of the Gospel is to pass on a written record of things which will allow any future reader to have the same life in His name as those who did receive Him. According to John, believing Jesus is the Christ, gives a reader a new life in His name which is the ability to become a child of God. By “believing in…” John states the reader is in the same condition as the writer of the Gospel and those who received Jesus Christ in the flesh.
The temporal component is the integral element in the two belief phrases of John 8:
As he was saying these things, many believed in him. So Jesus said to the Jews who had [in the past] believed him… (John 8:30-31)
The context, as He was saying… describes something taking place in the present where the perfect participle had believed… describes an antecedent action.2 This picture is unusual since the logical way to report a positive statement of what is believed in a setting of "as someone is speaking" is to report they “believed Him.”
After the woman was caught in adultery, John records Jesus making claims to be divine. He is sent by the Father (8:16); He is from above and not of this world (8:23); He makes two “I AM” statements (8:24, 28). Upon hearing these things, one expects to learn whether anyone believed Him. Yet John only reports many “believed in Him” never stating what obviously must also be true: they "believed Him."
The significance of this construction comes when the parenthetic statement which explains the meaning of “believed in Him” is considered:
On the last day of the feast, the great day, Jesus stood up and cried out, “If anyone thirsts, let him come to me and drink. Whoever believes in me, as the Scripture has said, ‘Out of his heart will flow rivers of living water.’” Now this he said about the Spirit, whom those who believed in him were to receive, for as yet the Spirit had not been given, because Jesus was not yet glorified. (John 7:37-39)
The many who believed in Him as He was saying these things would receive the Spirit later, after Jesus had been glorified. Therefore, John has recorded the events of Chapter 8 such that readers will find themselves in the same position as those who were physically present and actually heard Him. If the reader believes the written record, then they will receive the Spirit in exactly the same way as those who “believed in Him” as He was saying these things at the Feast of Booths. Those present as He was saying these things had to wait until Jesus was glorified; those reading do not wait because Jesus has been glorified.
A requirement to “believe Him” or to “receive Him” comes to an end once He is no longer on the earth. Thus John presented a written record of what Jesus said and is purposeful to do so in a way which gives every person who reads and believes in His name the same ability to become a child of God as those who did receive Him and those who did hear Him.
John ignores to "believe Him" as a means to receive the Spirit for three reasons:
- Those physically present must still wait until Jesus is glorified, a future action.
- It places readers who may only believe in Him in the same position as those who were physically present.
- Those who are present and believe Him may change and decide they do not believe Him, which is what happens at both the Feast of Booths and the Passover in Capernaum (John 6). Retrospectively, those who stopped following Him (Capernaum) or tried to kill Him (Jerusalem) are placed in a group of those who had believed Him and excluded from the group who believe in Him.
1. “Believed himself” or “himself believed” ἐπίστευσεν αὐτὸς is used in 4:53 in referring to the official from Cana after learning his son was healed.
2. Daniel B. Wallace, The Basics of New Testament Syntax, Zondervan, 2000, p. 267. When contrasted with a statement of belief “as He was saying these things…” a statement of what was believed in the past, casts doubt on what this group believes about those things He just said.