Adam Clarke on Psalms 71:19

Thy righteousness - is very high - עד מרום ad marom - is up to the exalted place, reaches up to heaven. The mercy of God fills all space and place. It crowns in the heavens what it governed upon earth.

Who hast done great things - גדלות gedoloth. Thou hast worked miracles, and displayed the greatest acts of power.

Who is like unto thee! - מי כמוך mi camocha. God is alone, - who can resemble him? He is eternal. He can have none before, and there can be none after; for in the infinite unity of his trinity he is that eternal, unlimited, impartible, incomprehensible, and uncompounded ineffable Being, whose essence is hidden from all created intelligences, and whose counsels cannot be fathomed by any creature that even his own hand can form. Who is Like Unto Thee! will excite the wonder, amazement, praise, and adoration of angels and men to all eternity.