The Grandfather's Return
When a son was born to him, the ba'al teshuva was asked by his non-observant father to grant him the privilege of being the sandek at the brit mila. The son hesitated because of the ruling in Shulchan Aruch that one should give such an honor to a very righteous Jew. Upon hearing his son's hesitation the father vowed that if he could serve as sandek he would begin observing Shabbat.
Rabbi Eliyashiv ruled that the father should be given this honor because there could be no greater merit for the child than having his grandfather become observant because of him.