The salah needs to be filled with our heart, mind and soul, being fearful of standing in front of Allah, while humbly praising Him and aiming for jannah in the hereafter, in sha Allah. The khushu and khudu, the humility, the devotion, the submissiveness, the humbleness of our limbs, the alertness of our body parts, these are the required elements of a salah which Allah almighty will accept in the akhirah. The true essence and spirit of salah revolves around the presence of khushu and khudu, meaning inward and outward submission and devotion respectively, praising Allah and communicating with Him with our deepest interest and love. The heart remaining free of any worldly worries and tensions while our body exhibits submission of even the tiniest body part.