In Nahjul Balagha, sermon 226, you can see such words of Ali:
May Allah reward such and such man who straightened the curve, cured the disease, abandoned mischief and established the sunnah. He departed (from this world) with untarnished clothes and little shortcomings. He achieved good (of this world) and remained safe from its evils. He offered Allah’s obedience and feared Him as He deserved. He went away and left the people in dividing ways wherein the misled cannot obtain guidance and the guided cannot attain certainty.
Ibn Abil Hadeed al-Mutazili in his commentary of this book (3/12) said:
وقد وجدت النسخة التي بخط الرضى أبى الحسن جامع (نهج البلاغة) وتحت (فلان) عمر ،
There is a copy written by ar-Razi Abul Hasan (which) gathered Nahjul Balagha, (where) under so and so (written) Umar.
Muhammad Jawad al-Mughniyah in “Fi zilal Nahjul Balagha” (3/p 330) said:
قيل: المراد بفلان أبو بكر. وقيل: عمر، وهو الأشهر
And it was said that under so and so (he) mean Abu Bakr, and it was said that (is about) Umar, and that is more famous.