But thou O Lord
'Adonay (ad-o-noy')
the Lord (used as a proper name of God only) -- (my) Lord.
art a God
'el (ale)
strength; as adjective, mighty; especially the Almighty (but used also of any deity)
full of compassion
rachuwm (rakh-oom')
compassionate -- full of compassion, merciful.
and gracious
channuwn (khan-noon')
gracious -- gracious.
longsuffering
'arek (aw-rake')
long -- long(-suffering, -winged), patient, slow (to anger).
'aph (af)
the nose or nostril; hence, the face, and occasionally a person; also (from the rapid breathing in passion) ire
and plenteous
rab (rab)
abundant (in quantity, size, age, number, rank, quality)
in mercy
checed (kheh'-sed)
kindness; by implication (towards God) piety: rarely (by opposition) reproof, or (subject.) beauty
and truth
'emeth (eh'-meth)
stability; (figuratively) certainty, truth, trustworthiness -- assured(-ly), establishment, faithful, right, sure, true (-ly, -th), verity.