The last part extends the thoughts of ver. 12 to all the righteous. It does not name them, for it is needless to do so. Imagery and reality are fused together in this strophe. It is questionable whether there were trees planted in the courts of the Temple; but the psalmist's thought is that the righteous will surely be found there, and that it is their native soil, in which rooted, they are permanent. The facts underlying the somewhat violent metaphor are that true righteousness is found only in the dwellers with God, that they who anchor themselves in Him, as a tree in the earth, are both stayed on, and fed from, Him. The law of physical decay does not enfeeble all the powers of devout men, even while they are subject to it. As aged palm trees bear the heaviest clusters, so lives which are planted in and nourished from God know no term of their fruitfulness, and are full of sap and verdant, when lives that have shut themselves off from Him are like an old stump, gaunt and dry, fit only for firewood. Such lives are prolonged and made fruitful, as standing proofs that Jehovah is upright, rewarding all cleaving to Him and doing of His will, with conservation of strength, and ever-growing power to do His will.
Ver. 15 is a reminiscence of Deut. xxxii. 4. The last clause is probably to be taken in connection with the preceding, as by Cheyne ("And that in my Rock there is no unrighteousness"). But it may also be regarded as a final avowal of the psalmist's faith, the last result of his contemplations of the mysteries of Providence. These but drive him to cling close to Jehovah, as his sole refuge and his sure shelter, and to ring out _this_ as the end which shall one day be manifest as the net result of Providence--that there is no least trace of unrighteousness in Him.