It wouldn't be A Very Cellular Song by the Incrediblke String Band would it? Lyrics on that link I gave, with the lines

Lay down my dear sister
Won't you lay and take your rest
Won't you lay your head upon your saviours breast
And I love you but Jesus loves you the best
And I bid you goodnight, goodnight, goodnight,
And I bid you goodnight, goodnight, goodnight.

(Which is very likely a quote from a previously existing song.)