Chapter 5, Section 3 (פֶּרֶק ה׳ אוֹת ג׳)

3. Rabbi Yishma’el said (ג אָמַר רַבִּי יִשְׁמָעֵאל): all these songs were heard by Rabbi Akiva (כָּל הַשִּׁירוֹת הַלָּלוּ שָׁמַע רַבִּי עֲקִיבָא), when he descended to the Merkavah (כְּשֶׁיָּרַד לַמֶּרְכָּבָה), and he grasped and learned them before the Throne of His Glory (וְתָפַשׂ וְלָמַד לִפְנֵי כִסֵּא כְּבוֹדוֹ), as they were being sung before Him by His ministering ones (שֶׁהָיוּ מְשׁוֹרְרִין לְפָנָיו מְשָׁרְתָיו).