In theology textbooks, the term “calling” has a heavy dogmatic loading rooted in God’s election and displayed in his causing the “call” to come on your path in some fashion. This is not what Peter is talking about here. The term “call” is here the equivalent of duty. Given the goodness and mercy sinners have received from God through Jesus Christ (1 Peter 1:3–4; 1 Peter 2:10), it clearly follows that these sinners echo similar goodness and mercy to fellow sinners.
9 Do not repay evil for evil or reviling for reviling, but on the contrary, bless, for to this you were called, that you may obtain a blessing.