In their desire to relay the maximum amount of information with the minimum amount of words, the Talmudic Sages sometimes used a poetic turn of phrase to communicate a subtle message. We thus find in our gemara that they referred to a certain form of tumah ritual impurity with the term madaf in order to indicate that it was of a slighter nature than other forms of ritual impurity.

This term madaf is based on the word nidaf found in a Torah passage which describes the suffering which G-d declares He will inflict upon Jews for abandoning their religious responsibilities. Not only will they be exiled from their land but "I shall instill a fear in their hearts, in the land of their enemies, and they will feel pursued by the sound of a nidaf leaf from which they will flee as on fleeing from the sword and falling, although there is no one in pursuit." (Vayikra 26:36)

Nidaf, explain the commentaries, refers to the rustling sound made by the leaf of a tree when it is blown by the wind against another leaf. That such a slight, innocent sound can strike fear in the hearts of threatened people is illustrated in a story the Midrash tells of Rabbi Yehoshua ben Korcha.

"We were once studying between some trees," related this Sage, "when we heard the rustling of wind blown leaves. We were afraid that the enemy was approaching and fled for our lives. After a while we realized that no one was pursuing us and we wept that the curse in the Torah had come upon us."

It is this slight, rustling leaf representing physical danger which serves as a simile for a slight form of the spiritual danger of tumah.

In the Torahs account of the relationship between Yehuda, the son of the Patriarch Yaakov, and Tamar, the passage which speaks of the discovery that she was pregnant states that this happened in "around three months" (Bereishet 38:24).

This passage is cited by the Sage Sumchus in the name of Rabbi Meir as a hint to the fact that a womans pregnancy is discernible after three months from conception, with the halachic ramifications discussed in the previous mishna.

Although the very mention of three months offers such a hint as to the rule for women who have full-term nine-month babies, this does not exclude the possibility that the pregnancy of a woman who gives birth after seven months is discernible after only a third of that period. As Rashi points out, it may indeed be the case that the pregnancy of such a woman is discernible after only two and one third months, but we must assume that every expectant woman is of the majority who have full-term babies and we cannot accord her the halachic status of pregnancy until a full three months have passed since conception.

As regards Tamar herself, the Midrash, quoted by Rashi in his commentary on the Torah, states that she gave birth to her twin sons after only seven months. The passage describing this birth (ibid. 38:27) omits the phrase used in regard to the birth of Rivkas twin children that "her days leading to her giving birth were completed" (ibid. 25:24), to indicate that Tamars was not a full-term birth.

In regard to Tamar, therefore, the above-mentioned "around three months" is interpreted by the Midrash as meaning a part of the first and third months, for a total of two and a third months. Nevertheless, the very mention of three months serves as the hint sought by the Sages in regard to discerning the pregnancy of all women.