Psalms 3:2

Great men rise up against me Men great in Torah, great in wisdom, great in wealth, tall in stature, such as Saul; the children of Raphah; Doeg, and Ahitophel.

Ad-nai, how (mah): In the Holy Tongue [Hebrew], [the word mah (מה)] applies both to something honored/great and to something lowly/despised. For example: [great,] "How (mah) great are Your works!" (Psalm 92:6); [lowly,] "What (mah) is man that You are mindful of him?" (Psalm 8:5). And in this context (Psalm 3:2), it expresses wonder/astonishment ["How numerous..."]. And Israel [those involved in the rebellion] were divided concerning him [David] into three groups: Some of them were [general] foes (tzarim), such as the men of Benjamin [who harbored resentment from Saul's time, like Shimei ben Gera - cf. (II Samuel 16)]. And some of them were attackers (kamim), namely his [own] son [Absalom], and Amasa [Absalom's commander, David's nephew - cf. (II Samuel 17:25)], and [other] relatives. And there were others saying [expressing the sentiment mentioned in the next verse, v. 3]: that "He has fallen and will not rise again." [Identifying the third group as those who declared David's situation hopeless].

Lord, how are mine adversaries increased! – For even his son had turned against him for an enemy, and Amasa, his sister's son, was with Absalom, and the greater part of Israel, whose heart inclined after Absalom; and this is reason for the repetition.

Many they are that are rising up against me: – All were rising up against him and were taking counsel to fight against him; and Shimei ben Gera even, who dared to reproach him and to pelt him with stones.