R' Akiva stated three things; concerning two [the Sages] agreed with him, and concerning one they did not agree with him. Concerning a lime-worker's sandal [the Sages agreed] that it is suscept-ible to the tumah of midras.  [And the Sages also agreed with R' Akiva] con-cerning the remnants of an oven [that they must be at least] four [tefachim in size]. For [the Sages] used to say that three tefachim was sufficient, but they conceded to [R' Akiva].  And concerning one they did not agree with him, [namely,] concerning a chair from which two of its [seat] slats were removed, one next to the other, which R' Akiva declares susceptible to tumah contamination, but the Sages declare it not susceptible to tumah contamination.

He used to say: A father merits a son with beauty, with [physical] strength, with [material] wealth, with wisdom [in Torah], and with years. And [re-garding] the number of generations [that is] before Him; for that is the time set [by him]. As it is stated: He proclaimed the generations from the beginning. [For] although it is stated with regard to the redemption from Egypt: And they will serve them and they will oppress them four hundred years, it is also stated: And the fourth generation shall return here.