Musnad Ahmad 30:1279

Muhammad ibn Bishr narrated to us, Muhammad ibn ‘Amr narrated to us, Abu Salamah narrated to us, from Abu Hurairah, who said: The Messenger of Allah (ﷺ) said: "When Allah created Paradise and Hellfire, He sent Gabriel and said: 'Look at them and at what I have prepared for their inhabitants within them.' So he came and looked at them and at what Allah had prepared for their inhabitants within them. He returned to Him and said: 'By Your Might, no one who hears of it will fail to enter it.' So He commanded that it be veiled with hardships. He said: 'Return to it and look at it and at what I have prepared for its inhabitants within them.' He said: So he returned to it, and behold, it had been veiled with hardships. He returned to Him and said: 'By Your Might, I fear that no one will enter it.' He said: 'Go to the Hellfire and look at it and at what I have prepared for its inhabitants within them.' So he came to it and looked at it and at what He had prepared for its inhabitants within them, and behold, it was [piled] upon itself, one part over another. He returned and said: 'By Your Might, no one who hears of it will enter it.' So He commanded that it be surrounded with desires. He returned to Him and said: 'By Your Might, I fear that no one will be saved from it, but that he will enter it.'"