We have both in these verses. There is a threefold summons to sing unto the Lord, and a similar threefold summons to speak for the Lord. Such psalms as this never contemplate a religion which can be hid away and held in secret. The passionate love which breathes in this psalm must have vent or die. There is here no coming to the Lord by night, or being secretly a disciple for fear of the Jews, but the psalm is an open, full, joyous confession of the soul's delight in the Lord. And such confession takes this double form.

I. Song. This is called for:

1. Because our love to the Lord should be amongst those deep and intense feelings which demand the fullest utterance of which the soul is capable. Plain prose will serve for ordinary communications, but when the soul is deeply stirred, as it should be, by the love of God, then song becomes a necessity. See in the Scriptures how the rapt utterances of psalmist and prophet inevitably clothe themselves in poetical form.

2. Because it is so attractive. It tells of a glad, bright, winsome religion, of sunshine in the soul and joy in the heart, all which in this sad, weary, sin-stricken world cannot but be infinitely attractive. Therefore God would have his people sing.

3. And because it is the noblest form of utterance. Music and poetry combine to invest the soul's deepest and holiest thought in the most perfect garment of praise.

4. And the song is to be a new song. Every day is a new day, and brings with it material for a new song.

"New mercies, each returning day,
Hover around us while we pray;
New perils past, new sins forgiven,
New thoughts of God, new hopes of heaven."

5. And universal. This is our desire, and, if so, its expression commits us to do our best to unite "all the earth" in this song.

6. It is to be grateful. "Bless his Name." What abundant reason there is for such gratitude! Happy they who thus sing unto the Lord!

II. SERMONS. These also are called for - fervent, holy speech for God. Not necessarily set discourses such as we understand by sermons. These, but not these alone, nor these at all, if God has not given us the needed capacity; but God-prompted, loving words spoken for him - these all can speak, and should do so as opportunity is given. Such speech is described, as was the song, in a threefold way.

1. Showing forth God's salvation. And this from day to day. This can be done, and perhaps best done, by what we are and do - by our life as well as by our lips; yet let not the latter be silent, as they too often are, to our own and others' great loss.

2. Declaring his glory among the heathen. There is no need to go far away to find these heathen. They are all around us. Tell them of the glory of his character, his Word, his service, his Spirit dwelling within, his eternal rest by and by.

3. His wonders among all people. Not the good people only - it is easy to talk before them; but among the unsaved, tell them what a wonderful Saviour Jesus is. - S.C.

I. THE TIME SPECIFIED — "To-day if ye will hear His voice." This is the uniform time and tense of the Holy Ghost's exhortations. "Consecrate yourselves to-day to the Lord." "I command thee this thing today." "Son, go work to-day in My vineyard." Therefore, "To-day if ye will hear His voice, harden not your heart."

1. "To-day" is a time of obligation Every man is under a present necessity as a subject of God to obey his Lord today, and having rebelled against his God, every sinner is under law to repent of sin to-day.

2. Remember, also, that to-day is a time of opportunity. There is this day set before us an open door of approach to God. This is a very favoured day, for it is the Lord's day, the day of rest, consecrated to works of grace. Today our Lord Jesus rose and left the dead that He might declare the justification of His people. This is a day of good tidings, therefore I pray you to seize the golden moments.

3. Remember that it is a time limited (Hebrews 4:7). To-day will not last for ever; a day is but a day. When days are longest, shadows fall at last and night comes on. The longest life soon wanes into the evening of old age, and old age hastens to the sunset of the tomb.

4. A word of encouragement: it is a time of promise, for when God says to a man, Come to Me at such a time, He by that very word makes an engagement to meet him. He has made no appointment with thee to meet with thee to-morrow, but He has engaged to speak with thee to-day, if thou wilt hear His voice. Never shall one wait and say, like young Samuel, "Speak, Lord, for thy servant heareth," without God's speaking in words of love ere long.

II. THE VOICE TO BE REGARDED. "His."

1. Remember that the voice of God is the voice of authority. God has a right to speak to you; shall the creature refuse to hear the Creator? Shall those who are nourished and fed by Him turn a deaf ear to the Preserver of men? When He saith "to-day," who among us shall dare to say that he will not hearken to-day, but by and by?

2. It is the voice of love. How wooing are its tones!

3. It is the voice of power. Old man, the Holy Ghost saith still, "To-day, to-day"; and He that saith "to-day " can make to-day for thee a day of tenderness and melting, till you will be no longer like a stone.

4. It is a pledging voice. When He saith, "Seek ye the Lord while He may be found," He doth, as it were, covenant that He will be found of you. Listen, then, to His promising voice, His cheering voice; it will cast all unbelieving fear out of you, and drive away Satan better than David's harp drove the evil spirit out of Saul. God help you so to do.

5. The voice of God should be easy to hear; for "the voice of the Lord is powerful, the voice of the Lord is full of majesty."

III. THE EVIL TO BE DREADED. "Harden not your heart."

1. It will be a serious evil if you do. Under the sound of love's entreaties, within ear-shot of mercy's imploring tones, the sinner is hardening his heart. Sad work to harden one's heart against one's own welfare! Shall any man do this and go unpunished? What think you?

2. It is a greater sin in some than in others, for the Scripture quotes the instance of Israel (Hebrews 3:8). Some of you are the highly privileged as compared with others.

3. This dreadful sin can be committed in a great many ways. Some harden their hearts by a resolution not to feel, some by wishing to wait, some by getting into evil company.

4. This sin will bring with it the most fearful consequences. "He sware in His wrath, they shall not enter into My rest!" You wish to rest at last, you long to rest even now. But it cannot be till you yield to God. You are not at peace now, and you never will be if you harden your hearts.

( C. H. Spurgeon.)