As we learned on daf 2, a kometz – a fistful of flour – was taken from most of the meal offerings that were brought in the Temple and was placed on the altar. The first Mishna taught that in most cases, if this was done she-lo lishmah – with improper intentions – the meal offering remains a valid sacrifice, although it is not credited to the owner of the offering and he will have to bring a replacement for it.
On today’s daf, Rav teaches that if kemitza was done she-lo lishmah on the Minḥat HaOmer it is totally invalid, since the purpose of this minḥa was to permit the new harvest and it did not fulfill that purpose.
The Omer is a measure of grain. In this case it is used to refer to the measure of barley offered in the Temple on the sixteenth day of Nisan, that is, the day following the first day of Pesaḥ. The Omer was harvested on the night following the first day of Pesaḥ – even if it was Shabbat – from the newly ripe grain and was prepared as roasted flour. A handful was burned on the altar and the rest was eaten by the kohanim. Until the Omer had been brought, it was forbidden to eat the grain from the new harvest.
Rav’s ruling – which, as we will see, was disputed by other amora’im – is based on his own logic and not on any Biblical sources. It appears that Rav believes that the Minḥat HaOmer is basically similar to other meal offerings in that improper intentions should not affect its validity. Nevertheless, this meal offering differs from others, since most menaḥot could be viewed as voluntary sacrifices in the event that they cannot be credited to their owner for the purpose that he meant to bring them. The Minḥat HaOmer, however, served a specific purpose – to permit the new grain to be eaten – and there was no possibility of bringing such an offering voluntarily. Therefore, if it did not accomplish its purpose there was no reason for it and it becomes invalid.