I would take "tent" as a Biblical reference, with the meaning tabernacle – cf. Numbers 1.1:
"And Jehovah spake unto Moses in the wilderness of Sinai, in the tent of meeting, on the first day of the second month, in the second year after they were come out of the land of Egypt..."
Or Psalm 61:4, which the "Bible in Basic English" translates as:
"I will make your tent my resting-place for ever: I will keep myself under the cover of your wings."
The capitalisation of "His", etc., interestingly, is not Blake's own; cf. the original design for the poem.