Narrated by Shaqiq (RA): Hudhaifa (RA) saw a person who was not performing the Ruqu and Sijdah perfectly. He said to him, "You have not prayed and if you die then you would die on a religion other than that of Muhammad (ﷺ)." [१] Qatadah (RA) said, the Prophet (ﷺ) said, the worst thief is the one who steals the salat. Sahabis said, how to steal salat? The Prophet (ﷺ) said: He who does not complete his Ruqu and Sijdah. [२]

Reference: [१] बुख़ारी: ૭९१ [२] सहीह (अल्बानी)। मिश्कात: ८८५