It was Shabbos Parshas Shekalim in 5728 (1968), a Shabbos that Satmar chassidim have never forgotten, when the Satmar Rebbe ztz”l, author of the Divrei Yoel, collapsed after suffering a stroke.
 
The phone rang on Motzaei Shabbos in the Bostoner Rebbe’s home, and on the line were the household members of the Satmar Rebbe ztz"l, with a request.
 
It’s well known that the Bostoner Rebbe ztz”l was expert in medical matters, and the doctors in Boston respected his opinion very much, therefore, they asked him to convince one of the senior doctors in Boston, an expert in brain strokes who incidentally was the personal physician of President Eisenhower, to come to New York.

The Bostoner Rebbe ztz”l immediately called the doctor and asked him to travel to New York, but the doctor replied calmly that tomorrow is Sunday, and Sunday is a day off for him, and with all due respect, he can fly only on Monday.

The Bostoner Rebbe did not give up, and after long time of pleading and request, the Bostoner Rebbe said: "You now have a rare opportunity, which doesn’t happen to just anyone, to save the life of the holiest man on earth. Go to New York ... " but the doctor refused.
 
The Bostoner Rebbe ztz”l hung up, hoping that he would soon change his mind.
 
Not an hour passed, and the telephone in Bostoner Rebbe’s home rang again, and on the line was the doctor: "Rabbi, let’s take that plane now and fly to New York, but I have a condition: You, Rabbi, will have to come with me."

A few hours later the Bostoner Rebbe and the doctor landed in New York and immediately headed toward the hospital where the Satmar Rebbe ztz”l was.
 
The doctor treated the Satmar Rebbe ztz”l for several days until his condition stabilized. 

Later, the Bostoner Rebbe ztz”l asked him why he changed his mind, but the doctor would not tell him anything. And he did not explain why he demanded that the Bostoner Rebbe ztz"l would accompany him on his journey.