Grading: It is "sahih li-ghayrihi"; its narrators are thiqah, but the chain is "munqati'".
Technical note / Defect ('illah): Tawus did not hear this narration from Suraqah (may Allah be pleased with him), as is explicitly stated in the narration of Shu'bah with Imam Ahmad (29/ 17590).
Note / Clarification: The full name of Idris al-Awdi is "Idris bin Yazid bin Abd al-Rahman".

Reference / Source: Imam Ahmad (17582) and Ibn Majah (2977) recorded it via Mis'ar, and Imam Ahmad (17589, 17590) and al-Nasa'i (3774) via Shu'bah; both of them narrate it from Abd al-Malik bin Maysarah with this same chain.
Details of the narration: The wording of Mis'ar's narration is that the Messenger of Allah (peace and blessings be upon him) delivered a sermon in this valley and said: "Know that umrah has entered into hajj until the Day of Resurrection." The wording of Shu'bah's narration is that Suraqah asked: O Messenger of Allah! Is this umrah of ours for this year only or forever? He (peace and blessings be upon him) said: "Rather, forever."

Technical note / Defect ('illah): Dawud bin Yazid al-Awdi contradicted the other narrators (Musnad Ahmad: 17583): he gave the chain Abd al-Malik bin Maysarah al-Zarrad, from al-Nazzal bin Sabrah, from Suraqah, i.e. he mentioned al-Nazzal bin Sabrah in place of Tawus; and this narrator Dawud is "da'if".

Reference / Source: Al-Nasa'i (3775) recorded it via Malik bin Dinar from Ata' bin Abi Rabah that Suraqah said: The Messenger of Allah (peace and blessings be upon him) performed tamattu' and we performed tamattu' with him. We asked: Is this specifically for us or forever? He (peace and blessings be upon him) said: "Forever."
Technical note / Defect ('illah): Ata' did not hear from Suraqah (may Allah be pleased with him); the link between them is Jabir bin Abd Allah (may Allah be pleased with him).

Reference / Source: This narration was recorded by Imam Ahmad (14279, 14942), al-Bukhari (1785, 2505, 7230), Muslim (1216), Abu Dawud (1787), Ibn Majah (2980), al-Nasa'i (3773) and Ibn Hibban (3791, 3921) via the (correct) route Ata', from Jabir, from Suraqah.

Corroborating chains and supporting reports: In narrating from Jabir (may Allah be pleased with him), Ata' is corroborated by Abu al-Zubayr (Musnad Ahmad: 14116, 15163) and by Imam Muhammad al-Baqir (Musnad Ahmad: 14440, Ibn Majah: 3074).

Corroborating chains and supporting reports: On this topic there is also a narration from Abd Allah bin Abbas (may Allah be pleased with them both), recorded by Imam Ahmad (4/ 2115), Muslim (1241), Abu Dawud (1790) and al-Tirmidhi (932).

Grading: Imam al-Tirmidhi says that the hadith of Ibn Abbas (may Allah be pleased with them both) is "hasan".
Note / Clarification: The meaning of this hadith is that there is no harm in performing umrah during the months of hajj; this is the position of Imam al-Shafi'i, Imam Ahmad and Ishaq bin Rahawayh.

General principle: The people of the Jahiliyyah did not perform umrah during the months of hajj, but when Islam came the Prophet (peace and blessings be upon him) granted a concession for it and said: "Umrah has entered into hajj until the Day of Resurrection", i.e. there is no harm in performing umrah during the months of hajj.

Note / Clarification: The months of hajj are Shawwal, Dhu al-Qa'dah and the first ten days of Dhu al-Hijjah, and no one should enter ihram for hajj except in these months.
General principle: The "sacred months" (al-ashhur al-hurum) are four: Rajab, Dhu al-Qa'dah, Dhu al-Hijjah and Muharram. This was stated by many of the people of knowledge among the Companions and others.

Technical note / Defect ('illah): The author (al-Hakim) relied on the following two narrations in making Ka'b bin Malik the brother of Suraqah, but "wahm" (error) occurred in these narrations, as will be explained; the correct view is that Suraqah's brother is named "Malik bin Malik bin Ju'shum". See the detailed research in our work on "Musnad Ahmad" (29/ 17581).