The arm of the Lord is a recurring motif throughout Scripture, where it almost always refers to the earthly manifestation of God’s power, particularly as seen in the Exodus. Isaiah takes that image and adds other attributes to it:
Power is still central, but it’s now linked to blessing, salvation and to a person (the Suffering Servant). Salvation is in turn linked to justice, righteousness and wrath.
Tenderness is closely related to power and blessing, but I’m not sure how to represent the overlap between those three 😉
The verses referred to are: Isaiah 40:10-11; 51:5, 9; 52:10; 53:1; 59:16; 62:8; 63:5, 12.