The phrase "in seventh heaven" means to experience great joy or contentment. The expression also implies that there are seven heavens to be had, which is a common teaching among several religions.
Two of the oldest religions that teach seven heavens are Hinduism and the ancient Babylonian cult. In Hinduism, there are seven higher worlds and seven lower worlds; the earth is the lowest higher world. The six higher worlds above us are places of increasing wonder and delight where people who have accumulated good karma go after they die. When the dead have spent all the time their good deeds have earned them, they are reincarnated and return to earth. Those who live extraordinarily pious lives can break out of this cycle and experience Nirvana, a state of eternal existence.
The ancient Babylonians did not teach that the seven heavens were for humans. Rather, they divided the different heavens into seven levels of space between the earth’s atmosphere and the spirit of the heavens; beyond was the Zodiac. Each of the seven heavens was associated with a particular god and a celestial body: the moon, Mercury, Venus, Mars, the sun, Jupiter, and Saturn.
Historians aren’t sure when the Jews first learned of Babylon’s seven heavens; Abraham might have been exposed to such a belief before he left Ur, or Hebrew scholars may have learned of it while exiled to Babylon. Either way, rabbis adapted the myth, integrating it into the Talmud—their extra-scriptural writings. The Jewish “heavens,” associated with the same celestial bodies, contain a mix of people, angels, demons, Nephilim, and natural phenomena, the specifics changing with the teacher. As the astronomical and meteorological sciences have advanced, Jews have rejected a literal seven heavens and now see them as metaphorical—there’s no way hail could come to earth from Jupiter, after all.
Islam combines the seven heavens of Judaism with a story from Zoroastrianism. Hadith literature tells how Muhammad was taken on a journey through all seven heavens. In each heaven he met a character from the Bible or another prophet of Islam. Centuries before, the Zoroastrian priest Arta Viraf supposedly made a similar trip to heaven. In Islam and Zoroastrianism both, the heavens are levels of paradise reserved for increasingly devout worshipers.
Dante Alighieri combined Babylonian mythology with Christian metaphor when he wrote The Divine Comedy. In Dante’s epic poem, the seven celestial bodies represent ever more virtuous natures. Above these heavens, in which the righteous are rewarded after death, are four more levels. The last is Empyrean, the immaterial dwelling place of God.
The Bible says nothing that would validate a belief in seven heavens, but the word heaven itself has several meanings. The Hebrew for “heaven,” shamayim, only appears in the plural form and can mean “sky” (Genesis 1:8–9), “outer space” (Genesis 22:17), or “the place where God dwells” (Joshua 2:11). In the New Testament, the Greek ouranos can mean “the dwelling place of God” (Matthew 12:50) or “the sky” (Acts 10:11). And paradeisos (“paradise” or “garden”) can refer to the place where dead believers await resurrection (Luke 23:43), to where God dwells now (2 Corinthians 12:4), or to our eternal home (Revelation 2:7).
In 2 Corinthians 12:2 Paul says he knew a man (assumed to be himself—he is speaking in the third person) who went to the “third heaven.” The “third heaven” here simply means the spiritual dwelling of God, as opposed to the other two “heavens,” the atmosphere and outer space. The three “heavens” implied in 2 Corinthians 12:2 would be the three different realms that we call “the sky,” “outer space,” and the “spiritual heaven.”
In our vernacular, “seventh heaven” means “the best, happiest place to be,” but the Bible doesn’t give any indication that a seventh heaven actually exists. God promises He will not always live above us, but He will live with us in the New Jerusalem (Revelation 21). And although we will receive rewards according to our works (Revelation 22:12), the Bible never suggests that we’ll be segregated from each other.