Adam Clarke on Psalms 31:2

Bow down thine ear - Listen to my complaint. Put thy ear to my lips, that thou mayest hear all that my feebleness is capable of uttering. We generally put our ear near to the lips of the sick and dying, that we may hear what they say. To this the text appears to allude.

Strong rock - Rocks, rocky places, or caves in the rocks, were often strong places in the land of Judea. To such natural fortifications allusions are repeatedly made by the Hebrew poetic writers.