The unusual combination נגלות כּהגּלות is explained by Ewald (§240, e., p. 607) in this manner, that whilst, so far as the sense of the clause is concerned, the second verb ought to be in the infinitive absolute, they were both written with a very slight change of form in the infinitive construct; whereas others regard נגלות as an unusual form of the infinitive absolute (Ges. Lehrgeb. p. 430), or a copyist's error for נגלה (Thenius, Olsh. Gr. p. 600). The proud daughter of Saul was offended at the fact, that the king had let himself down on this occasion to the level of the people. She availed herself of the shortness of the priests' shoulder-dress, to make a contemptuous remark concerning David's dancing, as an impropriety that was unbecoming in a king. “Who knows whether the proud woman did not intend to sneer at the rank of the Levites, as one that was contemptible in her eyes, since their humble service may have looked very trivial to her?” (Berleb. Bible.)
Verses 21-22
David replied, “Before Jehovah, who chose me before thy father and all his house, to appoint me prince over the people of Jehovah, over Israel, before Jehovah have I played (lit. joked, given utterance to my joy). And I will be still more despised, and become base in my eyes: and with the maidens of whom thou hast spoken, with them will I be honoured.” The copula vav before שׂהקתּי serves to introduce the apodosis, and may be explained in this way, that the relative clause appended to “before Jehovah” acquired the power of a protasis on account of its length; so that, strictly speaking, there is an anakolouthon, as if the protasis read thus: “Before Jehovah, as He hath chosen me over Israel, I have humbled myself before Jehovah” (for “before him”). With the words “who chose me before thy father and all his house,” David humbles the pride of the king's daughter. His playing and dancing referred to the Lord, who had chosen him, and had rejected Saul on account of his pride. He would therefore let himself be still further despised before the Lord, i.e., would bear still greater contempt from men than that which he had just received, and be humbled in his own eyes (vid., Psa 131:1): then would he also with the maidens attain to honour before the Lord. For whoso humbleth himself, him will God exalt (Mat 23:12). בּעיני is not to be altered into בּעיניך, as in the lxx. This alteration has arisen from a total misconception
