Psalms 34:1

I will bless the Lord at all times
That is, ascribe blessing, give honour, praise, and glory to him, both as the God of nature and providence, for every temporal mercy; and that every day, and at all times in the day; since these are renewed every morning, and continue all the day long: and as the God of grace, for all spiritual blessings; and that continually, because these last always; they are irreversible, unchangeable, and without repentance; yea, saints have reason to bless God in times of adversity as well as prosperity, since it might have been worse with them than it is; they have a mixture of mercy in all, and all things work together for their good;

his praise [shall] continually [be] in my mouth;
not the "praise" of which God is the author, but of which he is the object; which is due unto him, and is given him on account of the perfections of his nature, and the works of his hands, and the blessings of his providence and grace; this, the psalmist says, should be in his mouth: his meaning is, that he should not only retain in his heart a grateful sense of the divine favours, but should express it with his lips; should both make melody in his heart to the Lord, and vocally sing his praise; and that "continually", as long as he lived, or had any being, ( Psalms 146:2 ) .