وَعَنْ جَابِرٍ رَضِيَ اللَّهُ عَنْهُ قَالَ: أَتَيْتُ النَّبِيَّ ﷺ فِي دَيْنٍ كَانَ عَلَى أَبِي، فَدَقَقْتُ الْبَابَ، فَقَالَ: «مَنْ ذَا؟» فَقُلْتُ: أَنَا، فَقَالَ: «أَنَا أَنَا»، كَأَنَّهُ كَرِهَهَا.
Translation: Jabir said that he came to the Prophet ﷺ concerning a debt owed by his father and knocked on the door. The Prophet ﷺ asked, “Who is it?” Jabir answered, “It is I.” The Prophet ﷺ repeated, “I, I,” apparently disliking that answer.
فَدَقَقْتُ الْبَابَ means “I knocked at the door”; مَنْ ذَا؟ means “Who is this?”; and أَنَا means “I.” The question sought to identify the visitor, something “I” alone did not accomplish.
Sources: Bukhari and Muslim