[NAME, COMPANY AND ADDRESS, ex.
John Smith
1234 First Street
Suite 567
Anycity, Anystate  85245]
 

Dear [NAME, ex. John Smith], 

I was deeply saddened to hear of [COLLEAGUE'S SPOUSE'S NAME, ex. Bill]'s death.

I hope that you will accept my most sincere sympathy and condolence. [COLLEAGUE'S SPOUSE'S NAME, ex. Bill] was admired and respect by everyone it is difficult to accept that [he / she] is not with us any longer. 

If there is anything I can do for you at this difficult time, please let me know.

Sincerely, 

[YOUR NAME, ex. Jill Jones]