Hadith 1:

عنه، عن أبيه، عن يونس، عن بكار بن أبى بكر الحضرمي، قال: سمعت أبا عبد الله يقول: لسيرة على بن أبى طالب في أهل البصرة كانت خيرا لشيعته مما طلعت عليه الشمس، إنه علم أن للقوم دولة، فلو سباهم لسبيت شيعته، قال: قلت: فأخبرني عن القائم، أيسير بسيرته؟ - قال: لا، لان عليا سار فيهم بالمن لما علم من دولتهم، وإن القائم يسير فيهم بخلاف تلك السيرة، لانه لا دولة لهم

Narrated that Abu Abdullah Imam Sadiq (عليه السلام) said,

"The conduct of Ali ibn Abu Talib (عليه السلام) among the people of Basra was better for His Shia's from all that upon which the sun shines. He knew that the people would have rulership, so if He were to make them prisoners, it would result in His Shia's becoming prisoners (in future under non shia rulership)". 

I (the narrator) said, "So, inform me about al-Qaim (عليه السلام), would He be adopting the way/method of Imam Ali (عليه السلام)?

The Imam (عليه السلام) said, "No, because Ali (عليه السلام) dealt with them in a gentle way as He knew that about their rulership, but al-Qaim (عليه السلام) would deal with them opposite to that, because they will not have any rule any more."

[Source: al-Mahasin, Vol. 2, Pg. 320 / Elal al-Sharae, Vol. 1, Pg. 150]

There are multiple narrations in Elal al-Sharae giving reasons as to why Imam Ali (عليه السلام) restrained from His enemies, below is one such narration:

عَنْ زُرَارَةَ قَالَ سَمِعْتُ أَبَا جَعْفَرٍ ع يَقُولُ إِنَّمَا سَارَ عَلِيٌّ (ع) بِالْكَفِّ عَنْ عَدُوِّهِ مِنْ أَجْلِ شِيعَتِنَا لِأَنَّهُ كَانَ يَعْلَمُ سَيَظْهَرُ عَلَيْهِمْ بَعْدَهُ فَأَحَبَّ أَنْ يَقْتَدِيَ بِهِ مَنْ جَاءَ بَعْدَهُ فَيَسِيرَ فِيهِمْ بِسِيرَتِهِ وَ يَقْتَدِيَ بِالْكَفِّ عَنْهُمْ بَعْدَهُ

Narrated that Imam Mohammad Baqir (عليه السلام) said, 

"Imam Ali (عليه السلام) restrained (held back) from His enemies for the sake of Our Shias, because He knew that they (evil rulers) will have upper hand over them (i.e. the shias) after Him, so He liked that the one who comes after Him follows His way and deals with them in the same way He acted and follow Him in restraining from the Shias after Him.

[Source: Ilal al-Sharae, Shaikh Sadooq, Vol. 1, Pg. 147]