II Samuel 22:35 Kabbalah

מְלַמֵּ֥ד יָדַ֖י לַמִּלְחָמָ֑ה וְנִחַ֥ת קֶֽשֶׁת־נְחוּשָׁ֖ה זְרֹעֹתָֽי׃

Who traineth my hands for war, So that mine arms do bend a bow of brass.

Read kabbalistic (mystical) interpretation of II Samuel 22:35: and classical mystical sources.