I have declared my ways. In the first part of this verse he affirms he had prayed sincerely, and had not imitated the proud, who, trusting to their own wisdom, fortitude, and opulence, make not God their refuge. That man is said to declare his ways to God, who presumes neither to attempt nor undertake any thing unless with His assistance, and, depending wholly on His providence, commits all his plans to His sovereign pleasure, and centers all his affections in Him; doing all this honestly, and not as the hypocrites, who profess one thing with their lips, and conceal another within their hearts. He adds, that he was heard, which was of great importance in making him cherish good hope for the future. In the second part of the verse he solemnly declares, that he holds nothing more dear than the acquiring of a true understanding of the law. There are not a few who make known their desires unto God, but then they would that he would yield to their extravagant passions. And, therefore, the prophet affirms that he desires nothing more than to be well instructed in God's statutes. This statement is strengthened by the next verse, in which he once more asks the knowledge of these to be communicated to him. In both passages it must be carefully observed, that with the law of God set before us, we will reap little benefit from merely perusing it, if we have not his Spirit as our internal teacher. Some expositors will have the word which I have translated, I will meditate, to be, I will entreat or argue, and thus the Hebrew term svch, shuach, is referred both to the words and thoughts. The latter meaning is most in accordance with the scope of the passage. I take the import of the prophet's words to be this: -- That I may meditate upon thy wondrous works, make me to understand thy commandments. We will have no relish for the law of God until he sanctify our minds, and render them susceptible of tasting heavenly wisdom. And from this disrelish springs indifference, so that it is a grievous thing for the world to give a respectful attention to the law of God, having no savor for the admirable wisdom contained in it. With great propriety, therefore, does the prophet pray that this way may be opened to him by the gift of knowledge. From these words we are instructed, that in proportion to the spirit of knowledge given to us, our regard for the law of God, and our delight in meditating on it, ought to increase.

I have declared my ways - That is, I have declared or recounted them to thee. I have made mention of my cares, troubles, anxieties, purposes. I have laid them all before thee, reserving or keeping back nothing.
And thou heardest me - Thou didst answer me. It is only when we declare all our ways before God, that we can hope he "will" hear us. It is right and proper that we should go before God with all our cares and troubles. There is nothing that gives us anxiety, of which we may not speak to him, however trivial it may seem to be - even as a child speaks to a mother of the smallest matter that troubles him. When this is done, we may be assured that God will not turn away from us, or disregard our cry.
"I told him all my secret grief;
My secret groaning reached his cars;
He gave my inward pains relief,
And calmed the tumult of my fears."
Teach me thy statutes - Make known to me thy will. Acquaint me with what thou wouldst have me to do. See Psalm 119:12.

I have declared my ways - ספרתי sipparti, "I have numbered my ways," I have searched them out; I have investigated them. And that he had earnestly prayed for pardon of what was wrong in them, is evident; for he adds, "Thou heardest me."

I have (b) declared my ways, and thou heardest me: teach me thy statutes.
(b) I have confessed my offences and now depend wholly on you.

I have declared my ways,.... That is, to the Lord; either the ways he had chose and desired to walk in, and not wander from, and therefore entreated help and assistance, guidance and direction, in them; or his sinful ways and actions, which he acknowledged and confessed, lamented and bewailed, and entreated the forgiveness of; or all his counsels and cares, his affairs and business, in which he was concerned, and which he declared and committed to the Lord, to be directed and assisted in; or all his wants and necessities, which he spread before him at the throne of grace; which he did not as though the Lord was ignorant of these things, but partly as knowing it was the will of God that he should be inquired of by his people, to do the things for them they want; and partly to ease his own mind, and encourage his faith and hope in the Lord;
and thou heardest me: and directed him in the way he should go, and what he should do; forgave him his sins, and supplied his wants;
teach me thy statutes; which he desired to learn and obey, in gratitude for being heard and answered by him; See Gill on Psalm 119:12;

My ways - My sins; and all my cares, and fears, and troubles.