Responsa for Bekhorot 97:24

הלכה כדברי המיקל באבל:

but where the same subject is dealt with,<span class="x" onmousemove="('comment',' As, for example, here in regard to redemption, where month is mentioned also in connection with the subject of a first-born. We can therefore draw the analogy between the expressions month mentioned in connection with the law of the first-born laid down for generations and month mentioned in connection with the census of the Israelites' first-born in the wilderness, since both deal with an identical subject.');">²²</span>

Teshuvot Maharam