For 3,000 years, the eternal city of Jerusalem has held the most exalted position in the Jewish religion and a place of unparalleled importance in Jewish life and history.
First and foremost, King Solomon built the first Holy Temple in Jerusalem between the years 965 and 928 BCE. The people of Israel would come to the Holy Temple to pray and to give thanks, but especially to perform sacrifices on the three festivals of pilgrimage: Passover, Shavuot, and Succot. But in the year 586, the Babylonian monarch Nebuchadnezzar invaded Jerusalem, destroyed the Holy Temple, carried off its implements made of precious metals and exiled the Jews of Jerusalem to Babylon.
Although Nebuchadnezzar had laid waste to the Holy Temple, its holiness remained, and it was then the Jewish exiles swore: "If I forget you Jerusalem, may I forget my right hand and may my tongue adhere to the roof of my mouth if I do not remember, if I do not hold Jerusalem above my greatest joy." Generations of Jews have kept this vow to the present day. The nation of Israel longingly remembered the holiness of Jerusalem throughout thousands of years of exile.
The strong, heartfelt desire of every Jew to see Jerusalem rebuilt in his lifetime and the centuries-deep Jewish affection for the city King David founded are embodied in many important customs and prayers from Judaism’s great sages. For example, this prayer – "And to Jerusalem, your city mercifully return, and dwell within it as you said. And build in it soon in our lifetimes, the building for eternity, and may it hold a place for King David’s throne" – is repeated by every praying Jew several times a day.
In brief, Jerusalem is the holiest city in Judaism is because, in the 5,000-year span of Jewish religious life, the nation’s devotion to God has intersected more with this city and more intensely than it has with any other.
Various factors make Jerusalem holy to Muslims.
The historian Daniel Pipes wrotw in the Middle East Quarterly:
“The first Umayyad ruler, Mu’awiya, chose Jerusalem as the place where he ascended to the caliphate; he and his successors engaged in a construction program – religious edifices, a palace, and roads – in the city. The Umayyads possibly had plans to make Jerusalem their political and administrative capital[.] … But Jerusalem is primarily a city of faith. As the Israeli scholar Izhak Hasson explains, the "Umayyad regime was interested in ascribing an Islamic aura to its stronghold and center."
Toward this end (as well as to assert Islam’s presence in its competition with Christianity), the Umayyad caliph built Islam’s first grand structure, the Dome of the Rock, right on the spot of the Jewish Temple, in 688-91. The next step the Umayyads took to make Jerusalem holy to Islam relates to a passage in the Koran (17:1) that describes Muhammad’s Night Journey to heaven: "Glory to He who took His servant by night from the Sacred Mosque to the furthest mosque [al masjidi al aqsa]."
Pipes explains that when this Koranic passage was first revealed, in about 621, a place called the "Sacred Mosque" already existed in Mecca. "In contrast," he goes on, "the ‘furthest mosque’ was a turn of phrase, not a place. Some early Muslims understood it as metaphorical or as a place in heaven."
In other words, the line about the furthest mosque in the Koran is just a figure of speech. This means that there is no basis for associating the furthest mosque – the Koranic location of the start of Muhammad’s Night Journey – with the city of Jerusalem.
In 715, Pipes writes, the Umayyads did something very clever. To build up the prestige of their domain, they built a second mosque in Jerusalem, again on the Temple Mount, and named this one the "Furthest Mosque" (i.e., al-masjidi al-aqsa), the exact same name written in the holy Koran. And in so doing, the Umayyads forced the city of Jerusalem to assume a role in the life of the prophet Muhammad – a role which it never had. This is how the Muslim belief in the holiness of Jerusalem, which persists to this day, originated.
As Pipes points out, moreover, "it had the hugely important effect of giving Jerusalem a place in the Koran post hoc which naturally imbued the city with a higher status in Islam." This is another way of saying, that before the Umayyads built the Dome of the Rock and al-Aksa, Jerusalem had no status at all in Islam.
These days, the never-ending cry for a Palestinian state with Jerusalem as its capital surely contains a trace of the claim that the city is holy in Islam. But, essentially, the historic record shows that the actions and circumstances on which the claim is based aren’t very holy at all. In fact, by any standard of religious values in any society in the world, artificially imbuing a place with holiness, through wordplay and administrative sleight of hand, constitutes the very opposite of holiness.