As we shown before SAHIH hadith that Hassan[ra] defended the door of Uthman[ra], so that killers can’t reach Uthman[ra]: click here.
Now lets see more hadiths which shows the depression of Ali[ra] when Uthman[ra] was murdered & his love & honor for him:
Ali (ra) rushed to Uthman’s (ra) house after the news reached him and he couldn’t believe his eyes [that uthman[ra] was killed], he said some harsh words to the young companions guarding the door (including his two children):
كيف قتل عثمان وأنتم على الباب؟ ولطم الحسن، وكان قد جرح
“How did they kill Uthman while you were guarding the door!? and he hit his son al-Hassan even though he was wounded“.
source: Ibn abi ‘Asem al Ahad wal Thamani 1/125 from “Khilafat Ali” p87.
On that day he said angrily to the people who were present there fully knowing that some of them claimed that He had called for this murder:
تبًا لكم سائر الدهر، اللهم إني أبرأ إليك من دمه أن أكون قتلت أو مالأت على قتله
“May eternal Harm befall you! O Lord I am innocent from his blood, I did not participate nor did I order anyone to Kill him (As they falsely claimed)“.
source: Musannaf ibn Abi Shaybah 15/209. & hadith is SAHIH.
وروى الحاكم بإسناده عن قيس بن عباد قال : سمعت علياً رضي الله عنه الله عنه يوم الجمل يقول : اللهم إني أبرأ إليك من دم عثمان ولقد طاش عقلي يوم قتل عثمان ، وأنكرت نفسي وجاءوني للبيعة ، فقلت والله إني لأستحي من الله أن أبايع قوماً قتلوا رجلاً قال فيه رسول الله صلى الله عليه وسلم (( ألا استحيي ممن تستحيي منه الملائكة )) وإني لأستحيي من الله أن أبايع وعثمان قتيل على الأرض لم يدفن بعد فانصرفوا ، فما دفن رجع الناس فسألوني البيعة فقلت اللهم إني مشفق مما أقدم عليه ثم جاءت عزيمة فبايعت فلقد قالوا : يا أمير المؤمنين فكأنما صدع قلبي ، وقلت : اللهم خذ مني لعثمان حتى ترضى
al-Hakim narrated with its Isnad from Qays bin Ubad: I heard Ali may Allah be pleased with him say on the Day of Jamal: (( O Lord I seek refuge in you and I am innocent from the blood of Uthman, I had almost lost my mind the day he was murdered, I denied myself and they came to me offering a pledge of allegiance, I said to them: By God I feel shy from Allah that I would receive a pledge of allegiance from those who killed the Man that the Prophet PBUH described as: “Should I not feel shy of a man of whom the angels are shy?”, and I feel shy from Allah that I would receive allegiance while Uthman is murdered and still lying on the ground without burial. They left me and came back after he was buried asking me for the Baya’ah(Pledge of allegiance), I said: “O Lord I feel pity from what I am about to do” later came determination and I took the pledge when they said: “O chief of believers” I felt my heart ache and I said: “O Lord take from me and give to Uthman until you are pleased.” ))
-al-Mustadrak (3/95) and he said: SAHIH on the condition of Bukhari and Muslim, Imam al Dhahabi agreed with him.
-al-Bidayah wal Nihayah (7/202).
-al-Riyadh al-Nadirah (3/69,70).
-al-Sawa’eq al-Muhriqah p173.