וַיֹּ֣אמֶר אֵלָ֗יו קְחָ֥ה לִי֙ עֶגְלָ֣ה מְשֻׁלֶּ֔שֶׁת וְעֵ֥ז מְשֻׁלֶּ֖שֶׁת וְאַ֣יִל מְשֻׁלָּ֑שׁ וְתֹ֖ר וְגוֹזָֽל׃
And He said unto him: ‘Take Me a heifer of three years old, and a she-goat of three years old, and a ram of three years old, and a turtle-dove, and a young pigeon.’
Read Kabbalistic (mystical) interpretations of Genesis 15:9: Zohar and classical Jewish mystical sources, free online.