Surah 51. Az-Zariyat, Ayah 25

Lit., "unknown people' - i.e., not realizing that they were angels.

They were angels, who appeared suddenly before him at his tent-door in the guise of men, and saluted him with the salutation of peace. He returned the salutation, but felt, from their appearance and their manner, that they were unusual, not ordinary, strangers.

Munkar: unknown, uncommon, unusual, not customary, (hence by derived meaning, not applicable here, not fair or just); opposite in both primary and secondary meanings to maraf, well-known, usual, customary, just. Cf. xv. 62.