Rashi is informative. I'll copy paste it here from http://www.chabad.org/library/bible_cdo/aid/9997
He said: The Lord came from Sinai: Moses initiated his blessing by praising the Omnipresent, and then he addressed the needs of Israel. — [Sifrei 33:2] The praise with which Moses commenced, mentions the merit of Israel. All this was a way of conciliation, as if to say, “These people are worthy that a blessing should rest upon them.”
came from Sinai: He came out toward them when they came to stand at the foot of the mountain, as a bridegroom goes forth to greet his bride, as it is said, “[And Moses brought the people forth] toward God” (Exod. 19:17). We learn from this, that God came out toward them (Mechilta 19:17).
and shone forth from Seir to them: [Why did He come from Seir?] Because God first offered the children of Esau [who dwelled in Seir] that they accept the Torah, but they did not want [to accept it].
He appeared: to them [Israel]
from Mount Paran: [Why did God then come from Paran?] Because He went there and offered the children of Ishmael [who dwelled in Paran] to accept the Torah, but they [also] did not want [to accept it]. — [A.Z. 2b]
and came: to Israel.
with some holy myriads: With God were only some of the myriads of His holy angels, but not all of them, nor [even] most of them. This is unlike the manner of a mortal, who displays all the splendor of his riches and his glory on his wedding day. — [Sifrei 33:2]
a fiery law for them: It was originally written before God in [letters of] black fire upon [a background of] white fire. — [Tanchuma Bereishith 1] He gave it to them on tablets, inscribed, [as it were,] by His right hand [thus it is said here, “from His right hand”]. Another explanation of אֵשׁ דָּת : As the Targum renders it, that He gave it to them from amidst the fire.
