Sforno on Exodus 3:1/ספורנו על שמות ג׳:א׳

1ויבא אל הר האלוקים חורבה. Moses, all by himself; he wanted to pray and meditate there in complete isolation and concentration. The phrase is similar to Numbers 13,22 ויבא עד חברון, where we find that one of the spies, Calev, reportedly, came to Chevron. [the sudden singular ויבא instead of ויבואו, there prompted the sages to say that Calev went to pray at the graves of the patriarchs. Ed.]