Who knoweth the interpretation - פשר pesher, a pure Chaldee word, found nowhere else in the Bible but in the Chaldee parts of Daniel. "A man's wisdom maketh his face to shine." Every state of the heart shines through the countenance; but there is such an evidence of the contented, happy, pure, benevolent state of the soul in the face of a truly pious man, that it must be observed, and cannot be mistaken. In the Hebrew the former clause of this verse ends the preceding chapter. Who has ever been deceived in the appearance of the face that belonged to a savage heart? Those who represent, by painting or otherwise, a wise man, with a gravely sour face, striking awe and forbidding approach, have either mistaken the man, or are unacquainted with some essential principles of their art.
The boldness of his face shall be changed - Instead of ישנא yeshunne, which signifies shall be hated, many of Kennicott's and De Rossi's MSS. have ישנה yeshunneh, shall be changed or doubled. Hence the verse might be read, "The wisdom of a man shall illuminate his face; and the strength of his countenance shall be doubled." He shall speak with full confidence and conviction on a subject which he perfectly understands, and all will feel the weight of his observations.
And who - Rather, and as he who knoweth. The possessor of wisdom excels other people: it imparts serenity to his countenance, and removes the expression of gloom or fierceness (see the marginal reference).