Psalm 130:5

I wait for the Lord
For his gracious presence and the light of his countenance, being in darkness, as well as in the deep; for his salvation and deliverance out of the depths of distress; for an answer of prayer, having cried unto him for application of pardoning grace he had some view and hopes of; and for the performance of promises the Lord had made to him; and for eternal glory and happiness: all which are to be patiently and quietly waited for, God having his set time to do them; and may be confidently expected, since he is gracious and merciful, wise and powerful, faithful and immutable. David might also be waiting for the coming of Christ, as all the Old Testament saints did; through whom all the above are enjoyed;

my soul doth wait;
which shows that this was not mere bodily service or waiting upon God and for him in an external way; but expresses the intenseness of his mind, the earnest desires of his heart after God, his affection for him, and the exercise of all other graces on him; his whole soul, and all the powers of it, were engaged in this work;

and in his word do I hope:
both in his essential Word the Messiah, who was the Hope of Israel as well as the Saviour of them; the object, ground, and foundation of hope, of all blessings, of grace and of glory: and in his word of promise concerning the coming of Christ, and salvation by him; concerning the pardon of sin through him, and eternal life by him; as well as in many other special and particular promises made to David, concerning himself, his family, and his kingdom. Arama and Kimchi interpret it of the promise of deliverance from captivity made to the Jews.