Nay! If you knew with a sure knowledge (the end result of

﴿كـَلَّا لَوۡ تَعۡلَمُونَ عِلۡمَ ٱلۡيَقِينِ ﴾
[التَّكاثُر: 5]

Nay! If you knew with a sure knowledge (the end result of piling up, you would not have occupied yourselves in worldly things)

﴿كلا لو تعلمون علم اليقين﴾ [التَّكاثُر: 5]

Al Bilal Muhammad Et Al
No, were you to know with certainty of mind

Ali Bakhtiari Nejad
No way, if you knew the sure knowledge (you would know that)

Ali Quli Qarai
Indeed, were you to know with certain knowledge

Ali Unal
No indeed! If only you knew with certainty of knowledge (then you would not disorder priorities)

Hamid S Aziz
Nay! Did you but know with certain knowledge

John Medows Rodwell
Nay! would that ye knew it with knowledge of certainty

Literal
No but if you know knowledge (of) the assurance/certainty

Mir Anees Original
No, if you know (having) the knowledge that is certain

Mir Aneesuddin
No, if you know (having) the knowledge that is certain