This appears to be a letter which Benjamin wanted his children to read upon his death. He wanted to ensure that they accepted Christ as savior and know that they would have eternal life in Heaven. You can read it here.
November 29, 1819
To: James Harris, Richfield, NY
From: Joseph & Jane Griffeth, Westchester, CT
The letter was folded to form its own envelope and the return address portion appears to read West Chester, CT. In a different handwriting someone had written New London Co Conn. It is unknown if Joseph or Jane wrote the letter. The letter states that he/she was pleased to hear from him and learn they were all alive. Also heard from “my sister” and was pleased to hear that they were all alive also, although he/she doesn’t expect to ever see them again in this world. Has been troubled with Santana’s fire since last summer. The children are well. Amasa is in Lexington, Kentucky — has been gone four years next February.
I received A letter from you which gave Me Grate Pleasure to hear from you and to hear that you was All a live. We have Ben sick the Most of the time Sence you was hear and are out of health Now. I was very glad to hear from My Sister to hear that they was all a live & Alltho I Donte Never Expect to See them a gain in this world a gain and If we Should Bee So happy as to Meet in that Blessed world of Spirits that would Bee a happy Meeting. I have Bin troubled with the Santinas fire Since Last Sumer and cant git Noo Relief. Pray write to My Sister and let them No that we are a live. My Children are well for what I Now. Amasa is in Lexington in Kentucky. He has Bin gone fore years Next febuary.
I wrote him a letter to Night
Pray Burn these
To James Harris
November the 29 1819
 Perhaps he was referring to St. Anthony’s fire, or erysipelas, named so because the affected skin areas are bright red in appearance. It is a contagious skin disease, due to Streptococci, and accompanied by high fevers, shaking, chills, fatigue, headaches, vomiting, and general illness