The Prophet ﷺ said, "The first thing for which a servant will be brought to account on the Day of Resurrection is his prayer. If he has performed it completely, it will be recorded for him as a perfect deed. If he has not performed it completely, Allah, glorified be He, will say to His angels, 'Look, do you find any voluntary prayers for My servant?' Then they will use them to make up what was deficient in his obligatory prayer. After that, the rest of his deeds will be reckoned in the same manner."
عن النبي ﷺ قال: أول ما يحاسب به العبد يوم القيامة صلاته، فإن أكملها كتبت له نافلة، فإن لم يكن أكملها، قال الله سبحانه لملائكته: انظروا، هل تجدون لعبدي من تطوع؟ فأكملوا بها ما ضيع من فريضته، ثم تؤخذ الأعمال على حسب ذلك.
Ibn Majah (1426), Abu Dawud (866), and Hakim (1/262-263) all narrated it through Hammad bin Salama, from Dawud bin Abu Hind, from Zurara bin Awfa, from Tamim Dari, and mentioned it. Except that Abu Dawud did not mention its wording, but instead referred to the hadith of Abu Hurairah before it. Its chain of transmission is sahih. Hakim said, "It is a sahih corroborating witness meeting the criteria of Muslim."There are other hadiths on this subject mentioned in the Book of Prayer.