Tafsīr al-Qummi: From him, from Saʿdān bin Muslim:

From Abī ʿAbd Allāh عليه السلام: I (the narrator) asked him about al-Ṣirāt,1 whereupon he replied: It is thinner than a hair and sharper than the sword. And among them would be one who would pass over it like the lightning, and among them would be the one who would pass over it like the galloping horse, and among them would be one who would pass over it like walking, and among them would be one who would pass over it crawling – clinging on. So the fire would take some from it and leave some.

1. al-Ṣirāt (الصراط) is the bridge, hair-line in width, which everyone will have to pass through it on the Day of Judgement.

وعنه : عن سعدان بن مسلم ، عن أبي عبدالله ( عليه السلام ) ، قال : سألته عن الصراط ، قال : « هو أدق من الشعر ، وأحد من السيف فمنهم من يمر عليه مثل البرق ، ومنهم من يمر عليه مثل عدو الفرس ، ومنهم من يمر عليه ماشيا ، ومنهم من يمر عليه حبوا ، متعلقا ، فتأخذ النار منه شيئا وتترك بعضا » .