Ata bin Yasar reported,
A man came and spoke ill of Ali and Ammar 
in the presence of Ayesha.She said, "As for Ali, I will say nothing to you about him. But as for Ammar, I heard the Messenger of Allah say, 'He is never given a choice between two matters except that he chooses the more rightly guided of them.'"
Azami 10288
Sahihعن عطاء بن يسار قال
جاء رجل فوقع في علي وفي عمار رضي الله عنهما عند عائشة، فقالت: أما علي فلست قائلة لك فيه شيئا، وأما عمار فإني سمعت رسول الله يقول: لا يخير بين أمرين إلا اختار أرشدهما.
Tirmidhi (3799), Ibn Majah (148), and Ahmad (24820) narrated it, and Hakim graded it sahih (3/388), all of them through routes from Habib bin Abu Thabit, from Ata bin Yasar, who said, then he mentioned it. Its isnad is sahih, and the wording given here is that of Ahmad.As for what was narrated from Ashtar, who said, "There were words between Ammar and Khalid bin Walid, so Ammar complained about him to the Messenger of Allah ﷺ, and the Messenger of Allah ﷺ said, 'Whoever shows enmity to Ammar, Allah 
shows enmity to him, whoever hates him, Allah hates him, and whoever curses him, Allah curses him.'" Salama said, "This, or something similar." So despite the soundness of its isnad, its wording contains something objectionable, for cursing cannot be attributed to Allah , since it implies a deficiency, and Allah is free of any deficiency.Ahmad (16821) and Abu Dawud Tayalisi (1252) narrated it, both through the route of Shuba, from Salama bin Kuhayl, "I heard Muhammad bin Abdul-Rahman narrating from Abdul-Rahman bin Yazid, from Ashtar," who said, then he mentioned it. The apparent form of this isnad is disconnected, but it has been transmitted as fully connected through Shuba's route.Nasai narrated it (8212), and Hakim graded it sahih (3/389, 390), both through routes from Shuba, from Salama bin Kuhayl, "I heard Muhammad bin Abdul-Rahman bin Yazid narrating from his father, from Ashtar, from Khalid bin Walid," who said, the Messenger of Allah ﷺ said, "Whoever shows enmity to Ammar, Allah shows enmity to him, and whoever curses Ammar, Allah curses him."Ashtar's name was Malik bin Harith Nakhai.As for what Ahmad (16814), Nasai in Kubra (8211), Ibn Hibban (7081), and Hakim (3/390) narrated, all of them through the route of Yazid bin Harun, "Awwam bin Hawshab informed us, from Salama bin Kuhayl, from Alqama, from Khalid bin Walid," who said, "There were words between me and Ammar bin Yasir, and I spoke harshly to him. So Ammar went off to complain about me to the Prophet ﷺ. Khalid then came while Ammar was complaining about him to the Prophet [[r9])." He said, "Khalid kept speaking harshly to him, growing only harsher, while the Prophet ﷺ sat silent, saying nothing. Ammar wept and said, 'O Messenger of Allah, do you not see him?' The Messenger of Allah ﷺ raised his head and said, 'Whoever shows enmity to Ammar, Allah shows enmity to him, and whoever hates Ammar, Allah hates him.'" Khalid said, "So I left, and nothing was dearer to me than Ammar's approval, so I met him and he was pleased with me." This report is defective.Abu Hatim and Abu Zura were asked about this hadith of Awwam, and they said, "Awwam dropped several narrators from this isnad. Shuba narrated it from Salama, from Muhammad bin Abdul-Rahman, from his father, from Ashtar." See, Ilal al-Hadith (2588).