Helpful Article on Sefirat HaOmer

Here.

On the question of the status of Sfirat Ha’omer today we find three different opinions in the Rishonim. Most Rishonim are of the opinion that nowadays the mitzvah of Sfirat Ha’omer is only of rabbinic origin. On the other end of the spectrum we find the Rambam (Tmidim U’musafim 7/22,24) who is of the opinion that mitzvat Sfirat Ha’omer is Mideorita even in the absence of a Mikdash and the bringing of Omer. According to Rabenu Yerucham the counting of days is mideorita at all times while the counting of weeks is mideorita at the time of the Mikdash and only of rabbinic origin today. The rational behind this distinction is that the passuk which mentions the Omer speaks of “U’sfartem…sheva shabatot”, count seven shabatot, namely weeks not days. The next passuk which states “tisperu chamishim yom”, count fifty days, does not speak of the Omer at all.