I am a Pastor and one of my church members asked me to write a recommendation for his wife to show it to US counselor when his wife apply for US Visa....

I am a Pastor and one of my church members asked me to write a recommendation for his wife to show it to US counselor when his wife apply for US Visa. He is here in America and his wife still lives in India. He is currently admitted in the hospital and he wants his wife to be with him. His wife needs to apply US visa. Having a good recommendation from Pastor will boost her chance of getting visa. so that she can be with her loving husband here in USA. Her husband condition is not getting better. I have no idea how to write a good recommendation letter. Basically, this letter is for US counselor to explain the situation and to convince the US counselor to give US visa for his wife. In a nutshell, it's a recommendation letter. There is no word limit but you have to cover the things that I mention above.