We have already provided the proof from Nissaie that the Holy Prophet (pbuh) said anybody abused Ali abused me. Please check the link from Nissaie.

This is well proven that Moawiya bin Abu Sufyan involved in cursing Imam Ali (as), the hadith about Saad bin Abbi Waqas, we can also find in Sahih Muslim chapter virtues of Imam Ali. Please check this link for Sahih Muslim.

English Translation:

Sayyidina Sad ibn Abu Waqas (RA) narrated: Mu’awiyah ibn Abu Sufyan ordered Sa’d and asked,

“What prevents you from abusing Abu Turab.”

He said,

“As long as I remember three things that Allah’s Messenger had said I will not speak against him, for, even each of them is dearer to me than red camels. I heard Allah’s Messenger (SAW) say (this) to Ali while he had left him behind in one of his battles. Ali said to him,

“0 Messenger of Allah do you leave me behind with women and children?”

He said to him,

“Does it not please you that you be to me of the rank of Harun to Musa except that there is no prophethood after me.”

And I heard him say on the day of Khaybar,

“I will give the banner to a man who loves Allah and His Messenger and Allah and His Messenger love him.”

 We all hoped to receive that. But, he sent for Ali and he came. He had pain in his eyes. The Prophet (SAW) put his saliva in them and handed over the banner to him.

Then Allah gave us victory at his hands and revealed this verse

“We will summon our sons and your sons, and our women and your women. (3:61)”

Imam Tirmidhi graded this as Hassan Sahih Hadith