וַיִּקַּ֤ח מֹשֶׁה֙ חֲצִ֣י הַדָּ֔ם וַיָּ֖שֶׂם בָּאַגָּנֹ֑ת וַחֲצִ֣י הַדָּ֔ם זָרַ֖ק עַל־הַמִּזְבֵּֽחַ׃
And Moses took half of the blood, and put it in basins; and half of the blood he dashed against the altar.
Read kabbalistic (mystical) interpretation of Exodus 24:6: and classical mystical sources.