The definition of the sahaba

            From Anas (raa), he was asked (is there any one among
          the companions of Muhammad left after u), he (raa)
          said (some beduins remained who saw him (saaw), but
          the ones whom accompanied him and invaded with him
          no).
          The hadith is narrated by Ibn Saad, Ibn Al Salah said
          (its isnad is good), and al sayooti said (bi'isnad
          hasan).
          On this meaning, the majority of the scholars of usuls
          went that the person will not be a sahabi unless he
          lives with the messenger (saaw) for enough period of
          time.
          On the other hand, the opinion of the majority of the
          scholars of the hadith that the one who saw him (saaw)
          and believed in him , he is a companion. Then these
          differed will a person who saw him, then became a
          muslim after his death, a sahabi? Then some of them
          said even if he saw him from a far distance, he is a
          sahabi. And comes in the definition of the muhaditheen
          for the sahabi , the jin because the they had filled
          the requirements.
          And the basis of the definition is the word (sahabi)
          in arabic language, since the shairah did not put a
          special meaning for it, then we have to go with the
          linguistic meaning for the word. And the arabic
          language dictates in the urf (use)that enough period
          of friedship needed for companionship, and there is no
          cosideration in this regard for the later scholars
          whom tried to revolve around and claim that
          companionship does not need a period of mulazama
          (close friendship).
          If u see this, then the haqq is with the scholars of
          usuls.
          and it was narrated from Saaed Ibn Al Mussaiab (the
          imam of the followers) he said (we used not to
          consider a person from the companions except if he
          lived with the messenger for one or two year OR he
          invaded with him one or two battles).
          And it was mentioned that some of the tabieen used to
          narrate from some people who saw the messenger (saaw),
          then they they were not from the sahaba.
          And the goal of the scholars of the hadith is that
          they want to add the virtue of the companionship to
          any one who saw the hnorable face of the messenger
          (saaw), so that a group of people whom the messenger
          (saaw) witnessed for them with the virtue will not go
          out from companionship like jareer Ibn Abdillah al
          bujli and others.
          On the other hand, the usuli scholar he is the one who
          establishes rules and fundemantals of the deen, sice
          the sahaba are the ones who gave us the shariah, and
          transmitted the quraan and alone their ijmaa is
          devine.
          The imam said, the messenger (saaw( said (allah had
          chosen my companions over all people except the
          prophets).
          Allah swt said (the early ones of muhajiroun and
          ansar...allah is pleased with them and they are
          plesaed with allah).
          and this exclusive purification does not apply excxept
          to the sahaba.
          The imam said (and his words are taken from abu zarah)
          (and the sahaba are better than all others, and they
          are better than all the ones will come. This is
          because the deen is haqq and allah is haqq, and those
          who gave us this deen are the sahaba. And those who
          slander the sahaba, they are slandering our
          witnesses). (may be i misused the words).