Reference for Niddah 40:2
אמר רבי יוחנן
all others are not so wise. R. Johanan remarked: The wisdom of R. Hanina caused me not to examine any blood, for when I declared any unclean he declared it clean and when I declared it clean he declared it unclean. R. Eleazar remarked: R. Hanina's modesty is the cause of my examining blood. [For I felt] if R. Hanina who was modest allowed himself to be involved in doubt and examined blood, should not I examine it? R. Zera remarked: The Babylonian coinage was the cause of my refusing to examine blood; for I thought: If I do not understand the coinage system would I understand the nature of blood? This then implies that capability to examine blood depends on an understanding of the coinage; but did not Rabbah in fact understand the coinage system and yet did not understand the qualities of blood? — He was really drawing an inference a minori ad majus: If Rabbah who understood the coinage system refused to examine blood, should I<span class="x" onmousemove="('comment',' Who do not understand the coinage system. ');"><sup>2</sup></span>