It is also, though probably metaphorically (but possibly in a literal sense, since the psalm describes pilgrims on their way up to the Temple), a key word in the Psalms.
Psalm 24 asks (verse 3), mi ya’aleh b’har HaShem, “Who may ascend the mountain of the Lord?”
The answer (verse 4) is threefold: the person who has clean hands and a pure heart, and has not sworn deceitfully.
Three human faculties are the sign of a good person – their hand, their heart and their mouth.
What you do, what you feel, and what you say, are the key to ascending the Divine mountain – and like the four elements in the arba’ah minim on Sukkot, all must be taken together. As Kohelet (Ecclesiastes) says at the end of his book, sof davar, hakkol nishma – “The end of the matter (is) that hakkol, ‘everything’ is heard”.
A person can’t be good with only one or two parts of their being. The whole person is what is assessed from On High – the whole person working together as one.
The heart feels, the mouth articulates the thought, the hand carries it out. The holistic life is the way up the mountain.