Although offering clarified butter in the sacrificial fire in the name of the demigods, without the knowledge of the demigods he also offered oblations to the demons because they were his relatives through his mother.
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
स एव हि ददौ भागं परोक्षमसुरान् प्रति । यजमानोऽवहद्भागं मातृस्नेहवशानुगः
sa eva hi dadau bhāgaṃ parokṣamasurān prati | yajamāno'vahadbhāgaṃ mātṛsnehavaśānugaḥ
SB 6.9.3