וַ֭יִּרְעֵם כְּתֹ֣ם לְבָב֑וֹ וּבִתְבוּנ֖וֹת כַּפָּ֣יו יַנְחֵֽם׃
이에 저가 그 마음의 성실함으로 기르고 그 손의 공교함으로 지도하였도다
Midrash Tehillim
The correct spelling is "וירעם" and it means "and his heart trembled". Rabbi Abbahu said in the name of Rabbi Yochanan that one should sit and contemplate so that he will not take a turn guarding with his friend in the field. Rabbi Yudan Meshkalisa said that David sang to God with all kinds of instruments, what does it say in the end? "Let the praise of God be in their throats, and a two-edged sword in their hands" (Psalm 149:6), this refers to God's instrument, the sword.