Responsa for Bava Batra 14:16
כי אתא לקמיה דרבי יוחנן אמר ליה מאי טעמא לא תימא ליה מהא (שיר השירים ח, י) אני חומה ושדי כמגדלות אני חומה זו תורה ושדי כמגדלות
and that they are more in number than the sand? Seeing that of the whole of Israel it is written that they shall be like the sand on the sea shore,<span class="x" onmousemove="('comment',' Gen. XXII, 17. ');"><sup>25</sup></span> how can the righteous alone be more than the sand? — What the verse means, however, is I shall count the deeds of the righteous and they will be more in number than the sand. If then the sand which is the lesser quantity protects [the land] against the sea, how much more must the deeds of the righteous, which are a larger quantity, protect them? When Resh Lakish came before R. Johanan, the latter said to him: Why did you not derive the lesson from this verse, I am a wall and my breasts are like towers,<span class="x" onmousemove="('comment',' Cant. VIII, 10. ');"><sup>26</sup></span> where 'I am a wall' refers to the Torah, and 'my breasts are like towers'
Teshuvot Maharam
A. Matters of taxation depend on local custom. It is needless to ask me the custom of our community, for you may have a different custom. Anyone who settles in a new place is bound by the custom prevailing there. But since the community has completely settled its obligations to the burghers, by consenting to pay the tax to A, before Leah settled in T, the representatives of the community must prove through witnesses who are not residents of T, that according to their custom Leah was obliged to pay the amount the community demanded, before they could deprive her of any of her property. If Leah, however, rented a house in T before the tax was levied, she is bound to pay her share of the tax, despite the fact that the community may not be able to prove any prevailing custom to that effect.
SOURCES: Pr. 995. Cf. Menahem of Merseburg, Nimmukim (8).