Adam Clarke's Commentary on the Bible

Verse 3 (Psalms 1:3)

Like a tree planted - Not like one growing wild, however strong or luxuriant it may appear; but one that has been carefully cultivated, and for the proper growth of which all the advantages of soil and situation have been chosen. If a child be brought up in the discipline and admonition of the Lord, we have both reason and revelation to encourage us to expect a godly and useful life. Where religious education is neglected, alas! what fruits of righteousness can be expected? An uncultivated soul is like an uncultivated field, all overgrown with briers, thorns, and thistles.

By the rivers of water - מים פלגי palgey mayim , the streams or divisions of the waters. Alluding to the custom of irrigation in the eastern countries, where streams are conducted from a canal or river to different parts of the ground, and turned off or on at pleasure; the person having no more to do than by his foot to turn a sod from the side of one stream, to cause it to share its waters with the other parts to which he wishes to direct his course. This is called "watering the land with the foot," Deuteronomy 11:10 ; (note), where see the note.

His fruit in his season - In such a case expectation is never disappointed. Fruit is expected, fruit is borne; and it comes also in the time in which it should come. A godly education, under the influences of the Divine Spirit, which can never be withheld where they are earnestly sought, is sure to produce the fruits of righteousness; and he who reads, prays, and meditates, will ever see the work which God has given him to do; the power by which he is to perform it; and the times, places and opporttmities for doing those things by which God can obtain most glory, his own soul most good, and his neighbor most edification.

His leaf also shall not wither - His profession of true religion shall always be regular and unsullied; and his faith be ever shown by his works. As the leaves and the fruit are the evidences of the vegetative perfection of the tree; so a zealous religious profession, accompanied with good works, are the evidences of the soundness of faith in the Christian man. Rabbi Solomon Jarchi gives a curious turn to this expression: he considers the leaves as expressing those matters of the law that seem to be of no real use, to be quite unimportant, and that apparently neither add nor diminish. But even these things are parts of the Divine revelation, and all have their use, so even the apparently indifferent actions or sayings of a truly holy man have their use; and from the manner and spirit in which they are done or said, have the tendency to bear the observer to something great and good.

Whatsoever he doeth shall prosper - It is always healthy; it is extending its roots, increasing its woody fibres, circulating its nutritive juices, putting forth fruitbuds, blossoms, leaves, or fruit; and all these operations go on in a healthy tree, in their proper seasons. So the godly man; he is ever taking deeper root growing stronger in the grace he has already received, increasing in heavenly desires, and under the continual influence of the Divine Spirit, forming those purposes from which much fruit to the glory and praise of God shall be produced.

- Adam Clarke's Commentary on the Bible