The saga highlighted a "shared vulnerability" in an interconnected world, Rt Rev Nicholas Holtam said in the message, which features in his 2018 Christmas card.
Bishop Nicholas told Premier: "What it did - as well as damage individuals - is damage a community, it's damaged our trust in one another.
"This is a time to rebuild trust - and to have confidence in who we are and what we are."
The Declaration, which is being sent to more than 800 people, asserts that "love, light and life will triumph" in Salisbury.
It also pays tribute to those "who risked themselves and responded with courage, dedication and skill".
The poisonings began on 4th March 2018 with the targeting of a former Russian spy and his daughter.
When Sergei and Yulia Skripal became ill after becoming exposed to Novichok, a police officer, Detective Sergeant Nick Bailey, was also contaminated.
On 30th June, two British nationals - Charlie Rowley and Dawn Sturgess - also fell ill due to Novichok. Sturgess died on 8th July.
Bishop Nicholas told Premier: "One of the things I want to come from [the letter] is [to highlight] that good can come out of bad things.
"Salisbury's had a difficult year but we can use the experience and build on it, not just for our own sakes but to saying something to the world."
In April, Bishop Nicholas took part a special service to celebrate community life in the city and to pray for "cleansing" over the site where a former Russian spy was targeted in a nerve agent attack.
The Salisbury Declaration of Hope in full says: "For Salisbury, 2018 has been a difficult year. We have been reminded of our shared vulnerability and the interconnectedness of world events.
"In Advent, as we wait again in darkness to celebrate the light of Christ,
"We affirm God's promise that goodness, love, light, and life will triumph.
"We hold in God's healing all who are hurt, directly and indirectly.
"We thank all who risked themselves and responded with courage, dedication and skill.
"We pray for the life and soul of our cathedral city, that it will prosper and be a beacon of Christian values.
"We commit ourselves to promoting justice, truth and trust.
"We will live in peace and renew our hope, here and throughout the world.
"We declare that we will work together to achieve this."
Click here to listen to Premier's Alex Williams speaking with the Bishop of Salisbury, Rt Rev Nicholas Holtam:
Stay up to date with the latest news stories from a Christian perspective. Sign up to our daily newsletter and receive more stories like this straight to your inbox every morning.