וְעָשִׂ֥יתָ מִזְבֵּ֖חַ מִקְטַ֣ר קְטֹ֑רֶת עֲצֵ֥י שִׁטִּ֖ים תַּעֲשֶׂ֥ה אֹתֽוֹ׃
And thou shalt make an altar to burn incense upon; of acacia-wood shalt thou make it.
Read kabbalistic (mystical) interpretation of Exodus 30:1: and classical mystical sources.