Shiva Purana
सौरैस्तु किरणैरेव होमारम्भाग्निमध्यगान्॥ निक्षिप्य होमसम्पूर्त्तौ भस्म संगृह्य गोपयेत् ॥ ८२ ॥
They were in the midst of the fire at the beginning of the sacrifice by the rays of the sun After the sacrifice is completed one should place the ashes and keep them hidden.
english translation
sauraistu kiraNaireva homArambhAgnimadhyagAn॥ nikSipya homasampUrttau bhasma saMgRhya gopayet ॥ 82 ॥
hk transliteration by Sanscript