Source and decoding - Taanit 2a
שְׁלֹשָׁה מַפְתְּחוֹת בְּיָדוֹ שֶׁל הַקָּדוֹשׁ בָּרוּךְ הוּא שֶׁלֹּא נִמְסְרוּ בְּיַד שָׁלִיחַ, וְאֵלּוּ הֵן: מַפְתֵּחַ שֶׁל גְּשָׁמִים, מַפְתֵּחַ שֶׁל חַיָּה, וּמַפְתֵּחַ שֶׁל תְּחִיַּית הַמֵּתִים.
Rabbi Yochanan: three keys are in God’s hand and were not given to a messenger: the key of rain, the key of childbirth, and the key of resurrection.
Rabbi Yochanan: three keys are in God’s hand and were not given to a messenger: the key of rain, the key of childbirth, and the key of resurrection. All three point to areas with no intermediary.