Jabir bin Samura reported,

The people of Kufa complained about Saad to Umar, so he removed him from his post and appointed Ammar over them. They continued to complain until they claimed that Saad did not even know how to pray properly. So Umar sent for him and said, "Abu Ishaq" (which was Saad's kunya), "these people claim that you do not know how to pray well."Abu Ishaq replied, "By Allah, I used to lead them in prayer just as the Messenger of Allah ﷺ prayed, without falling short of it in any way. I would pray the evening prayer, lengthening the first two units and shortening the last two."Umar said, "That is what I thought of you, Abu Ishaq."Then Umar sent a man, or two men, with him to Kufa to ask the people about him. He did not leave a single mosque without inquiring about Saad, and the people praised him favorably, until he entered a mosque belonging to Banu Abs. A man among them named Usama bin Qatada, whose kunya was Abu Sadah, stood up and said, "Since you have asked us under oath, I will tell you. Saad did not march with the army, did not distribute spoils equally, and was not just in his judgments."Saad said, "By Allah, I shall make three supplications. O Allah, if this servant of Yours is a liar and stood up out of showing off and seeking reputation, then prolong his life, prolong his poverty, and expose him to trials."After that, whenever the man was asked about himself, he would say, "I am an old man afflicted with trials. The supplication of Saad has struck me."Abdul-Malik said, "I saw him afterwards. His eyebrows had drooped down over his eyes from old age, and he would accost young girls in the streets and grope them."

عن جابر بن سمرة قال

شكا أهل الكوفة سعدا إلى عمر فعزله واستعمل عليهم عمارا، فشكوا حتى ذكروا أنه لا يحسن يصلي، فأرسل إليه فقال: يا أبا إسحاق ( كنية سعد) إن هؤلاء يزعمون أنك لا تحسن تصلي، قال أبو إسحاق: أما أنا والله فإني كنت أصلي بهم صلاة رسول الله ﷺ ما أخرم عنها، أصلي صلاة العشاء فأركد في الأوليين، وأخف في الأخريين، قال: ذاك الظن بك يا أبا إسحاق، فأرسل معه رجلا، أو رجلين، إلى الكوفة، فسأل عنه أهل الكوفة، ولم يدع مسجدا إلا سأل عنه ويثنون معروفا، حتى دخل مسجدا لبني عبس، فقام رجل منهم يقال له: أسامة بن قتادة يكنى أبا سعدة، قال: أما إذا نشدتنا فإن سعدا كان لا يسير بالسرية، ولا يقسم بالسوية، ولا يعدل في القضية. قال سعد: أما والله لأدعون بثلاث: اللهم إن كان عبدك هذا كاذبا قام رياء وسمعة فأطل عمره، وأطل فقره، وعرضه بالفتن، وكان بعد إذا سئل يقول: شيخ كبير مفتون، أصابتني دعوة سعد. قال عبد الملك: فأنا رأيته بعد قد سقط حاجباه على عينيه من الكبر، وإنه ليتعرض للجواري في الطرق يغمزهن.