John 3:13 And no man hath ascended up to heaven,

Nicodemus comes to Jesus by night. They discuss the nature of man's origin. Nicodemus asked how anyone is able to know these things himself.

KJV

John 3:13 And no man hath ascended up to heaven, but he that came down from heaven, even the Son of man which is in heaven.

NIV

John 3:13 No one has ever gone into heaven except the one who came from heaven—the Son of Man.

LISTENERS HEARD

And no one has ascended into the skies if not the one out of this sky descending, the Son of the man.

LOST IN TRANSLATION

The "ascend up/gone" and "came down" are both from the same root, a Greek word meaning "step" or "walk," but with different prefixes meaning "up" and "down." Our words "ascend" and "descend" are closer in feeling to the Greek. Strangely enough, the "ascended" is the past perfect tense, an action completed in the past, while the "descend" is something that happens at a point in time. The meaning is that Jesus ascended at some time in the past. The word translated as "ascended up" is a metaphor for "ascended into higher knowledge." That usage makes a great deal of sense here since Jesus just made the claim of understanding "heavenly things" in John 3:12.

The "has ascended" is into a plural word, "the skies," while the "descending" is from a singular word, "the sky."

First, the last phrase in the KJV, "which is in heaven," doesn't exists in the Greek sources used today. The phrase was originally added to the Latin Vulgate.

MY TAKE

Jesus had already ascended to the skies before descending from it.

GREEK (Each Word Explained Bottom of Page)

John 3:13 καὶ οὐδεὶς ἀναβέβηκεν εἰς τὸν οὐρανὸν εἰ μὴ ὁ ἐκ τοῦ οὐρανοῦ καταβάς, ὁ υἱὸς τοῦ ἀνθρώπου.

CW - Confusing Word -- The "to" does not capture the specific meaning of the word.
MW - Missing Word -- The word "the" before "heaven" is not shown in the English translation.
IW - Inserted Word -- The word "he" doesn't exist in the source.
CW - Confusing Word -- The "came" does not capture the specific meaning of the word. Nor is this word relaled to the word usually translated as "came."
WF - Wrong Form - The "came" is not an active verb but a participle, "descending."
MW - Missing Word -- The word "the" before "heaven" is not shown in the English translation.
IW - Inserted Word -- The word "even" doesn't exist in the source.
MW - Missing Word -- The word "the" before "man" is not shown in the English translation.
OS -- Outdated Source -- The Greek word translated as "which is in heaven" existed in the KJV Greek source but not the source we use today.

MW - Missing Word -- The word "and" before "no one" is not shown in the English translation.
IW - Inserted Word -- The word "ever" doesn't exist in the source.
WW - Wrong Word -- The word translated as "gone" should be something more like "ascended."
IW - Inserted Word -- The word "who" doesn't exist in the source.
CW - Confusing Word -- The "came" does not capture the specific meaning of the word. Nor is this word relaled to the word usually translated as "came."
WF - Wrong Form - The "came" is not an active verb but a participle, "descending."
MW - Missing Word -- The word "the" before "heaven" is not shown in the English translation.
MW - Missing Word -- The word "the" before "man" is not shown in the English translation.

EACH WORD of KJV

And -- The Greek word translated as "and" is used as the conjunction "and," but it also is used to add emphasis ("also").

no man -- The Greek word translated as "no man" also means "no one" and other negatives nouns.

hath -- This helping verb "hath" indicates that the verb is the tense indicating an action completed in the past.

ascended - "Ascended" means "to go up," "to ascend," "to mount," and "to turn up." It has a lot of specific meanings including "ascending to higher knowledge."

up - This is from the prefix of the verb.

to -- (CW) The word translated as "to" means "into" a place, "towards" as a direction, "in regards to" a subject, and "up to" limits in time and measure. The "into" of a place is meant here more than a direction.

missing "the" -- (MW) The untranslated word is the Greek definite article, which usually precedes a noun and, without a noun, takes the meaning of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those"). See this article for more.

heaven, -- (WN) The word translated as "heaven" means sky, the climate, and the universe. It also meant the home of the gods in a physical sense: the sun, moon, and planets were named for the gods. More about the word in this article. The word is not singular but plural here.

but - Two Greek words are translated as "but." Literally, they mean "if not" but this phrase is used to mean "except," "instead," and "but."

he -- (IW) There is nothing that can be translated as "he" in the Greek source. It was added because the next verb was translated as active rather than a participle.

that -- The word translated as "that" is the Greek definite article, without a noun, it has the sense of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more.

came -- (CW, WF) The verb translated as "came down" means "descend" or "go down" as we say in English that rain "comes down" not "goes down." It is not any word for "come." It is not an active verb but a participle, "descending."

down - This is from the prefix of the verb.

from -- The Greek preposition translated as "of" means "out of" or "from."

missing "the" -- (MW) The untranslated word is the Greek definite article, which usually precedes a noun and, without a noun, takes the meaning of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those"). See this article for more.

heaven, The word translated as "heaven" means sky, the climate, and the universe. It also meant the home of the gods in a physical sense: the sun, moon, and planets were named for the gods. More about the word in this article. Here the word is singular.

even -- (IW) There is nothing that can be translated as "even" in the Greek source.

the -- The word translated as "the" is the Greek definite article. The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those"). See this article for more.

Son -- The word translated as "son" more generally means "child" or "descendant." The phrase "the son of man" is the common way Christ refers to himself. It is discussed in detail in this article. Its sense may be "the child of the man."

of -- This word "of" comes from the genitive case of the following word that required the addition of a preposition in English. The most common is the "of" of possession, but it can also mean "belonging to," "part of," "which is," "than" (in comparisons), or "for," "concerning" or "about" with transitive verbs.

missing "the" -- (MW) The untranslated word is the Greek definite article, which usually precedes a noun and, without a noun, takes the meaning of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those"). See this article for more.

man - The Greek word for "man" means "man," "person" and "humanity" in the singular. In the plural, it means "men," "people," and "peoples."

which is in heaven. -- (OS) There is nothing in the Greek that can be translated as "which is in heaven" in the source we use today but it does exist in the source that the KJV translators used.

EACH WORD of NIV

missing "and" -- (MW) The untranslated word "and" is used as the conjunction "and," but it also is used to add emphasis ("also").

no one -- The Greek word translated as "no man" also means "no one" and other negatives nouns.

has -- This helping verb "has" indicates that the verb is the tense indicating an action completed in the past.

ever -- (IW) There is nothing that can be translated as "ever" in the Greek source.

gone - (WW) "Gone" means "to go up," "to ascend," "to mount," and "to turn up." It has a lot of specific meanings including "ascending to higher knowledge."

into -- The word translated as "to" means "into" a place, "towards" as a direction, "in regards to" a subject, and "up to" limits in time and measure. The "into" of a place is meant here more than a direction.

missing "the" -- (MW) The untranslated word is the Greek definite article, which usually precedes a noun and, without a noun, takes the meaning of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those"). See this article for more.

heaven, -- (WN) The word translated as "heaven" means sky, the climate, and the universe. It also meant the home of the gods in a physical sense: the sun, moon, and planets were named for the gods. More about the word in this article. The word is not singular but plural here.

except - Two Greek words are translated as "but." Literally, they mean "if not" but this phrase is used to mean "except," "instead," and "but."

the one who came from heaven—the Son of Man.-- The word translated as "that" is the Greek definite article, without a noun, it has the sense of "the one." The Greek article is much closer to our demonstrative pronouns ("this," "that," "these," "those") than the English "the." See this article for more.

who -- (IW) There is nothing that can be translated as "he" in the Greek source. It was added because the next verb was translated as active rather than a participle.