וְר֣וּחַ לָבְשָׁ֗ה אֶת־עֲמָשַׂי֮ רֹ֣אשׁ השלושים [הַשָּׁלִישִׁים֒] לְךָ֤ דָוִיד֙ וְעִמְּךָ֣ בֶן־יִשַׁ֔י שָׁל֨וֹם ׀ שָׁל֜וֹם לְךָ֗ וְשָׁלוֹם֙ לְעֹ֣זְרֶ֔ךָ כִּ֥י עֲזָרְךָ֖ אֱלֹהֶ֑יךָ וַיְקַבְּלֵ֣ם דָּוִ֔יד וַֽיִּתְּנֵ֖ם בְּרָאשֵׁ֥י הַגְּדֽוּד׃ (פ)
Then the spirit clothed Amasai, who was chief of the captains: Thine are we, David, And on thy side, thou son of Jesse; Peace, peace be unto thee, And peace be to thy helpers; For thy God helpeth thee. Then David received them, and made them captains of the band.
Read kabbalistic (mystical) interpretation of I Chronicles 12:19: and classical mystical sources.