Trim along the edges of a tear to remove jagged edges and loose threads. Paint both sides of the tear with no fray to stabilize the fabric. Allow the no fray to dry for 15 minutes.
Thread a curved upholstery needle with heavy duty thread.
Grip the needle with needle nose pliers and bring the point of the needle up through the fabric 1/4 inch beyond the end of the tear. Pull the thread through leaving 1 inch inside.
Turn both edges of the tear under so that good fabric is visible on both sides and the tear is pointed toward the inside (cushion filler) of the sofa. Bring your needle sideways so that it is facing across the tear. Pierce the good fabric, the folded-under part of the fabric on the first side of the tear, the folded-under part of the fabric on the second side of the tear and up through the good fabric. Pull the stitch snug but do not pull the tail of the thread out.
Cross over just below the entry point of your first stitch and repeat. Space your stitches about 1/8 inch apart and after the third stitch pull the fabric together snugly so that the torn opening is completely closed. Use this same stitch for closing seams.