The Gemara at the end of Ta’anis (30b) says: “R’ Akiva says: Anyone who does work on Tisha B’Av won’t see any blessing forever (אינו רואה סימן ברכה לעולם). The Chachomim say: Anyone who does work on Tisha B’Av, and doesn’t mourn over Yerusholayim, won’t merit to see it’s rejoicing”. From this Gemara, it would seem that we don’t rule like R’ Akiva who says, “one won’t see any blessing”, as the Chachomim argue on R’ Akiva and the rule is that when it’s R’ Akiva against the Chachomim we rule like Chachomim (see Eruvin 46b). However, practically it doesn’t seem like this.
Although the girsa [textual version] of Gemara is that the machlokes is between R’ Akiva and the Chachomim, the Rif, Rosh (end of Ta’anis) and Tur (end of 554) all have the girsa that R’ Gamliel is the one who says, “anyone who does work on Tisha B’Av won’t see any blessing forever” and not R’ Akiva, and they make no mention of the opinion of the Chachomim. If we change the girsa from R’ Akiva to R’ Gamliel we can understand how the halachah goes like R’ Gamliel, as the rule in Eruvin is specific to R’ Akiva. (The aforementioned Terumas HaDeshen and Beis Yosef (end of 554) point out the girsa change, but don’t offer any explanation.)
