Let all those that seek thee - All those who desire to know thee; to understand thy ways; to be thy friends. The phrase is used to denote the truly pious, because it is a characteristic of all such that they truly desire to be acquainted with God, and to find the way which leads to his favor.
Rejoice and be glad in thee -
(1) By finding thee, or securing the object which they sought;
(2) in thee, as the source of all true comfort and joy.
The prayer is that all such may be successful in their efforts, while those who have no such aim may be disappointed, Psalms 40:14.
Let such as love thy salvation -
(a) Thy method of salvation, or the appointed way by which men may be saved; and
(b) the salvation itself - deliverance from the guilt and dominion of sin, and complete and eternal restoration to the favor of God.
Say continually, The Lord be magnified - See the notes at Psalms 35:27, where the same expression occurs.