Ibn Ezra on the Torah

The nature of a ladder [sulam] is a symbol [semel], or it is an explanation of the Gematria valuation of 'Sinai' (Genesis Rabbah 68:12-14). And Rabbi Shlomo HaSefardi said that 'ladder' hints at the highest soul and 'G-d's angels' hints at wise thoughts. Rabbi Joshua said that the reason for the ladder is that his (Jacob's) prayer rose on it and his salvation from the heavens came down on it. These explanations do not explain it in light of the prophecy of Zecharia (1:8), Amos (7:1), and Jeremiah (1:11). The reason for the ladder here is a metaphor, for nothing is concealed from G-d. Worldly things hang onto the heavens as though there is a ladder between them, upon which the angels go up to report on things after they have been walking along the earth. Likewise, it is written that other angels descend to fulfill G-d's tasks, like a king with his servants.