לז"נ הקדושים הרב הגאון והצדיק ר' מרדכי יהודה בן הר' שמואל וכל משפחתו הי"ד

From my father A"H:

                                        

The posuk (Breishis 21 -2 ) says

 “Lamoed Asher Diber Oso Elokim”

Rashi says:

The  Malach  made a scratch on the wall and said that he will return   

the following year, when  the sun will be at the same spot,   and Soroh

will have a child.

 The malochim visited Avrohom  the first day of Pesach.

 Yitzchok was born the following year on the first day of Pesach.

Question:              

The timing is off  by 11 days!

It takes 365 days for the sun to return to the same  spot .  ( solar year).

From Pesach to Pesach the following year is only 354 days.

When the sun returned to the same spot it was 11 days after Yitzchok’s  birth.

 Answer:

The Malach did not return for Yitzchok’s birth. He returned 11 days later.

It is written in the seforim that Malach Refoel visits newborn boys 3 days after their bris .(gimmel lemiloso)  to heal them.

It was Malach Refoel  who  scratched  the wall  and  promised to  return exactly on the day when the sun will be at the same spot.

Malach Refoel   returned  to heal  Yitzchok  3 days after his bris

Yitzchock was born 354 days after the besura (Pesach-Pesach) plus 8 days

for the bris and 3 days (354+8+3=365)