Umar said to Saad, "The people have complained about you in every matter, even in the prayer."Saad replied, "I prolong the first two units and shorten the last two, and I do not fall short in following the prayer of the Messenger of Allah ﷺ."Umar said, "That is what I expected of you."
أخبرنا عمرو بن علي قال حدثنا يحيى بن سعيد قال حدثنا شعبة قال حدثني أبو عون قال سمعت
عمر لسعد قد شكاك الناس في كل شيء حتى في الصلاة فقال سعد أتئد في الأوليين وأحذف في الأخريين وما آلو ما اقتديت به من صلاة رسول الله ﷺ قال ذاك الظن بك
Bukhari transmitted it in the Book of adhan, chapter, "Lengthening the first two units of prayer and shortening the last two," hadith 770, and Muslim in the Book of Prayer, chapter, "Recitation in Dhuhr and Asr," hadith 159/453, from the narration of Shubah with this wording. It is also in Kubra, hadith 1074.