וַֽיַּחֲלֹ֗ם וְהִנֵּ֤ה סֻלָּם֙ מֻצָּ֣ב אַ֔רְצָה וְרֹאשׁ֖וֹ מַגִּ֣יעַ הַשָּׁמָ֑יְמָה וְהִנֵּה֙ מַלְאֲכֵ֣י אֱלֹהִ֔ים עֹלִ֥ים וְיֹרְדִ֖ים בּֽוֹ׃
And he dreamed, and behold a ladder set up on the earth, and the top of it reached to heaven; and behold the angels of God ascending and descending on it.
Read kabbalistic (mystical) interpretation of Genesis 28:12: and classical mystical sources.