יַֽעַנְךָ֣ יְ֭הוָה בְּי֣וֹם צָרָ֑ה יְ֝שַׂגֶּבְךָ֗ שֵׁ֤ם ׀ אֱלֹהֵ֬י יַעֲקֹֽב׃
The LORD answer thee in the day of trouble; The name of the God of Jacob set thee up on high;
Rashi on Psalms
May the Lord answer you on a day of distress This psalm was [composed] because he [David] would send Joab and all Israel to war, and he would stand in Jerusalem and pray for them, as the matter is stated (in II Sam. 18:3): “It is better that you be for us from the city as aid.” Were it not for David, Joab would not have succeeded in battle.
Rashi on Psalms
the name of the God of Jacob Who promised him [Jacob] when he went to Haran and kept His promise; therefore, it is stated: “the God of Jacob.”