Parshas Vayeira: Drush Shmuel - The Yud In Yitzchok Needs Some Work
The Medrash tells us that each letter of Yitzchok's name meant something. The "Yud" is for the Aseres HaDibros, the "Tzadi" for Sara, who was 90 years old at the time of his birth, the "Ches" since he was the first one who had a Bris Mils at 8 days old, and "Kuf" for Avrohom who was 100 years old.
The Pninim UParparaos brings a Remez to this from the Drush Shmuel. The Pasuk says (Vayeira 21:6) that when Yitzchok was born Sarah said "Tzchok Asa Li Elokim Kol HaShomei'a Yitzachak Li; Hashem made a Tzchok for me and whoever hears will become full of Tzchok. The first reference to Tzchok is Yitzchok without the Yud. This is because all the remazim in his name were realized at that time, except for the Aseres HaDibros which is represenyted by the Yud.
Tzchok Asa Li Elokim, the last three letters Hashem already did for Sarah. "Kol HaShomei'a Yitzachak Li," the Yud for the Aseres HaDibros will only be realized over time if they are fulfilled.
RS, Gateshead, 2010-10-24 11:03:27 See Rashi (17:19) who qoutes a Midrash that the Yud represents the 10 Nisyonos of Avrohom Ovinu. However Midrash Rabba (53:7) says as above that it refers to the 10 dibros.YH, 2010-10-24 14:16:31 Rashi in Lech Lecha on 17:19 says that the yud is for the ten tests.