Bukhari

Hadith Commentary:
The translation of the chapter heading is derived from the fact that Umar (radi Allahu anhu) was the Caliph at the time, yet he asked other Companions about this issue.
Now, the objection will not arise that since Umar (radi Allahu anhu) did not accept only the statement of Mughirah (radi Allahu anhu), how then can a solitary report (khabar wahid) be considered authoritative? It is indeed authoritative, as has been mentioned above, because Umar (radi Allahu anhu) requested a second testimony for the sake of further caution and firmness, not because a solitary report was not authoritative in his view. For even after the testimony of Muhammad bin Maslamah, it still remained a solitary report (khabar wahid).

Hadith Commentary:
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Hazrat Umar radi Allahu anhu was a rightly guided Caliph, and the Messenger of Allah sallallahu alayhi wa sallam had also declared him to be a muhaddath (one who receives inspiration) and mulham (one who is inspired). Despite this, when making judgments, he consulted with the scholars. Thus, in one case, he consulted Hazrat Mughirah bin Shu’bah radi Allahu anhu, asking, “Have you heard any hadith regarding this?” Furthermore, out of additional caution, he requested testimony regarding the hadith narrated by Hazrat Mughirah bin Shu’bah radi Allahu anhu.
In any case, according to Hazrat Umar radi Allahu anhu, a solitary report (khabar wahid) was considered proof.
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From this, it is also understood that judges must exercise extreme foresight and caution when deciding cases. They should not act hastily in this matter; rather, after thorough investigation, they should issue judgments in accordance with the Book and the Sunnah.
And Allah is the One whose help is sought.