You can find this exercise on page 266 of the book Synergistic Golf.
Exercise Type: YOGA-STRETCH
Exercise Category: ARMS - HANDS, CLUB CONTROL - ACCURACY, FLEXIBILITY
Kneel on all fours with knees and hands body width apart. Place palms on floor with fingers spread wide. Shift body weight slightly forward over hands pressing ends of fingers into the floor. Hold for 5 seconds then release and repeat 3x. Do not force stretch.