Albert Barnes Commentary 1 Kings 1:6

"And his father had not displeased him at any time in saying, Why hast thou done so? and he was also a very goodly man; and he was born after Absalom." — 1 Kings 1:6 (ASV)

Had not displeased him - That is, “His father had never checked or thwarted him all his life.”

A very goodly man - Here, too, Adonijah resembled Absalom (2 Samuel 14:25). The Jews, like other ancient nations, considered the physical qualities of rulers to be very important and wanted their kings to be remarkable for strength, stature, and beauty (1 Samuel 9:2). Adonijah’s personal advantages no doubt helped to draw the people to him.

His mother... - This means Haggith bore Adonijah after Maacah bore Absalom (2 Samuel 3:3–4). The words supplied by translators (often shown in italics) are not in the original text; for this reason, some suggest a slight alteration to the text, which would read, “David fathered him.”