For thy mercy
checed (kheh'-sed)
kindness; by implication (towards God) piety: rarely (by opposition) reproof, or (subject.) beauty
is great
gadowl (gaw-dole')
great (in any sense); hence, older; also insolent
unto the heavens
shamayim (shaw-mah'-yim)
air, astrologer, heaven(-s).
and thy truth
'emeth (eh'-meth)
stability; (figuratively) certainty, truth, trustworthiness -- assured(-ly), establishment, faithful, right, sure, true (-ly, -th), verity.
unto the clouds
shachaq (shakh'-ak)
a powder (as beaten small): by analogy, a thin vapor; by extension, the firmament -- cloud, small dust, heaven, sky.