Technical note / Defect ('illah): The manuscripts have the word "nu'ammu" (we used to lead the prayer) here, but the correct word is the one established from "Talkhis al-Dhahabi", which has been retained in the text.
Important point: The original wording in "al-Musannaf" is: "We used to be on military expeditions, and no one was appointed as commander over us except the Companions of the Messenger of Allah (peace and blessings be upon him)."

Grading: Its chain is strong (qawi).
Technical note / Defect ('illah): 'Asim bin Kulayb (bin Shihab) and his father Kulayb are both saduq (truthful), with no harm in them. However, there is disagreement from 'Asim about identifying the Companion of this narration: several narrators called him "al-Muzani", Shu'bah expressed doubt and said "al-Muzani or al-Juhani", while Sufyan al-Thawri explicitly named him "Mujashi' bin Mas'ud al-Sulami".
Important point: These narrations can be reconciled as follows: the commander of the army in that expedition was Mujashi' bin Mas'ud (may Allah be pleased with him) (a man of many conquests and campaigns), and he ordered this man from Muzaynah or Juhaynah to announce the rulings that were practised among the Companions of the Messenger of Allah (peace and blessings be upon him). In this way all the narrations agree.

Reference / Source: This hadith is in "Musannaf Ibn Abi Shaybah" (14/210).

Reference / Source: Al-Nasa'i narrated it (4457) via Abu al-Ahwas Sallam bin Sulaym, from 'Asim bin Kulayb, with this same chain, and in it he mentioned the words "a man from Muzaynah".

General principle: According to al-Azhari, the "jadha'" of goats is one year old and that of sheep eight months old. Ibn al-A'rabi says that "ijdha'" is the name of a stage (condition), not an age; thus a young female goat ('anaq) becomes a jadha' in a year, but sometimes, because of abundant pasture, it grows fat and becomes a "jadha'ah" before completing the year. A lamb born of young parents becomes a jadha' in six to seven months, and one born of old parents in eight to ten months.
Reference / Source: In the hadith of Abu Burdah bin Niyar (may Allah be pleased with him): "I have a young female goat that is a jadha'ah." Al-Khattabi says: that is why a jadha' of goats does not suffice (for sacrifice), since for goats nothing younger than a "thani" is valid, whereas the jadha' of sheep is valid.
Note / Clarification: A "thani" is an animal whose two front teeth have fallen out; among camels it is one that has completed five years and entered the sixth, among cloven-hoofed animals (cattle, goats, sheep) one that has completed two years and entered the third, and among solid-hoofed animals (horses) one that has completed three years and entered the fourth. In all kinds it is the stage after the "jadha'".

General principle: The majority of scholars, who hold that a jadha' of sheep is valid for sacrifice, differ on its age: (1) one that has completed a year and entered the second; this is the most correct view among the Shafi'is and the best known among the lexicographers. (2) Six months (half a year); this is the view of the Hanafis and Hanbalis. (3) Seven months; the author of "al-Hidayah" reported this from al-Za'farani. (4) Six or seven months; al-Tirmidhi reported this from Waki' bin al-Jarrah.

Reference / Source: For further detail see: al-Mutarrizi's "al-Mughrib fi Bayan al-Mu'rab" and "Fath al-Bari" (17/177).