This is added as the effect of these comfortable rains, that they fill the pastures with grass for cattle, and the valleys (which he mentions as the most fruitful places, though he doth not exclude the rest) with corn for the use of man. They shout for joy, they also sing, i.e. they are abundantly satisfied with thy goodness, and in their manner sing forth the praises and declare the goodness of their Creator and Benefactor. Compare Psalms 147:8. Such passions or actions as these are oft figuratively ascribed to lifeless creatures, both in sacred and profane poetical writings; which are said to rejoice or mourn, &c, when their condition is such as calls for rejoicing or mourning, and would cause them to do so, if they were capable of such actions
Related Commentaries of Psalms 65:13
Psalms 65:13
13 The pastures are clothed with flocks; the valleys also are covered over with corn; they shout for joy, they also sing.