The Gemurah in showing that the color of yellow is not a Triefa, brings the story of Rav Natan, in that a mother who had two previous children die of Bris Milah, bring him the third child to look at ( in the Rif and Rosh - it's the 4th child). He said to wait till the child gets more blood in him. The Tosfos comments that he must have held like Rebbie that two is a Chazukah. Why? What does this have to do with Chazukah? If this was the first child, and he was yellow, are we to assume you have to do the Milah Bezmanah ? only because two children already died , we can wait. If two children already died, why don't we say Chazukah, and not take a chance with the third child, and not give him a bris at all. If you will answer that he was only a little yellow, and not enough to postpone the milah for it, and that we give him a Bris later, because we can Toleh the deaths of the other two children because of this yellowness. Then today why do we postpone a Bris for even a little yellowness ?
Thank You,
Shmuel Katz
This question was asked to the Radvaz (2:826). The Radvaz replied that it is clear that Rebbi Nasan would have pushed the Milah off in general even if he would have held like Rebbi Shimon Ben Gamliel that a Chazakah is three times. In this case, Tosfos is saying that Rebbi Nasan held like Rebbi that the first two children, and any subsequent children, wouldn't die from the Milah but rather from the sickness they acquired before the Milah. This means that there was nothing indicating the child couldn't have a Milah, but rather that they couldn't have a Milah with this sickness. If he held like Rebbi Shimon, the Radvaz explains in Tosfos, we would have to suspect that the Milah itself might have caused the death, and the child would not be able to have a Bris Milah until he would grow older. This is how Tosfos knows that Rebbi Nasan holds like Rebbi.
Kol Tuv,
Yaakov Montrose