Charles H. Spurgeon on Psalms 89:17

For thou art the glory of their strength. Surely in the Lord Jehovah have we both righteousness and strength. He is our beauty and glory when we are strong in him, as well as our comfort and sustenance when we tremble because of conscious weakness in ourselves. No man whom the Lord makes strong may dare to glory in himself, he must ascribe all honour to the Lord alone; we have neither strength nor beauty apart from him. And in thy favour our horn shall be exalted. By the use of the word our the Psalmist identifies himself with the blessed people, and this indicates how much sweeter it is to sing in the first person than concerning others. May we have grace to claim a place among those in covenant with God, in Christ Jesus, for then a sense of divine favour will make us also bold and joyous. A creature full of strength and courage lifts up its horn, and so also does a believer become potent, valiant, and daring. The horn was an eastern ornament, worn by men and women, or at least is so at this day, and by the uplifting of this the wearer showed himself to be in good spirits, and in a confident frame of mind: we wear no such outward vanities, but our inward soul is adorned and made bravely triumphant when the favour of God is felt by us. Worldly men need outward prosperity to make them lift up their heads, but the saints find more than enough encouragement in the secret love of God.