Allah, may He be Glorified and Exalted, says (interpretation of the meaning), "Hasten towards forgiveness from your Lord and a garden as vast as the heavens and the earth, which is prepared for the pious." (Al ‘Imran 3:133) Ibn ‘Uthaymin said, “This is something that is indicated by the Qur’an and Sunnah, and Ahl al-Sunnah wa’l-Jama‘ah are unanimously agreed that Paradise exists at present. Hence Allah, may He be Glorified and Exalted, says (interpretation of the meaning), "Hasten towards forgiveness from your Lord and a garden as vast as the heavens and the earth, which is prepared for the pious." (Al ‘Imran 3:133) ‘Prepared’ means that it has been made ready. This indicates that it exists at present, just as Hell exists at present, and they will never cease to exist.” Allah, may He be Glorified and Exalted, says (interpretation of the meaning), "Then beware of the fire whose fuel is men and stones, which is prepared for the disbelievers." (al-Baqarah 2:24)

Al-Sam‘ani said, “which is prepared for the disbelievers means: it has been made ready for the disbelievers. This indicates that the Fire has been created, and it is not as the innovators say. It also indicates that it has been created for the disbelievers, even though some believers may enter it by way of punishment and requital for bad deeds.” ‘Abdullah ibn ‘Umar (may Allah be pleased with him) narrated that the Messenger of Allah (blessings and peace of Allah be upon him) said, "When one of you dies, he is shown his place morning and evening. If he is one of the people of Paradise, then (he is shown his place) among the people of Paradise, and if he is one of the people of Hell, then (he is shown his place) among the people of Hell. And it is said: This is your place, until Allah resurrects you to it on the Day of Resurrection.” Al-San‘ani said, “ ‘When one of you dies, he is shown his place’ that is, where he will reside, in Paradise or Hell. This indicates that Paradise and Hell are already created.”

Anas (may Allah be pleased with him) narrated that the Prophet (blessings and peace of Allah be upon him) said, “By the One in Whose hand is the soul of Muhammad, if you saw what I have seen, you would laugh little and weep much.” They said: What have you seen, O Messenger of Allah? He said: “I have seen Paradise and Hell.” (Muslim)

Scholarly views regarding this matter:
i. Ahmad ibn Hanbal said, “Paradise and Hell are already created; this is proven by reports from the Messenger of Allah (blessings and peace of Allah be upon him).”
ii. Tahir ibn Muhammad al-Isfarayini said, “… Paradise and Hell are already created. All of that is mentioned in the Qur’an and in clear reports from the Prophet (blessings and peace of Allah be upon him), in a manner that leaves no room for doubt, for one who is saved from stubbornness. Allah, may He be Glorified and Exalted, has clearly mentioned Paradise and Hell, and that they already exist, and that Paradise is prepared for the believers and Hell for the disbelievers. Adam (peace be upon him) was made to dwell in Paradise, then he was expelled from it and sent down to the earth. Moreover, it was narrated from the Messenger (blessings and peace of Allah be upon him) that he entered Paradise on the night of the Mi‘raj (ascent to heaven).”