Rinaldo Fabris, in a footnote (p. 347, n. 46) mentions a string of citations illustrating the importance of rain (in reference to his comments on Jas 5:17-18). One of the citations was to Jubilees 12:4, 18. Below is the text of Jubilees 12 according to Charles’ APOT:
1 And it came to pass in the sixth week, in the seventh year thereof, that Abram said to Terah his father, saying, ‘Father!’ 2 . . . , ‘What help and profit have we from those idols which thou dost worship, . . . ? . . . 4 Worship the God of heaven, Who causes the rain and the dew to descend on the earth And does everything upon the earth, And has created everything by His word, And all life is from before His face. . . .
Though his father does not react positively to Abraham’s revelation at first, Abraham does destroy all of the household idols. (He also marries Sarah here in the narrative. The theme of rain continues, however:
16 And in the sixth week, in the fifth year thereof, Abram sat up throughout the night on the new moon of the seventh month to observe the stars from the evening to the morning, in order to see what would be the character of the year with regard to the rains, and he was alone as he sat and observed. 17 And a word came into his heart and he said: All the signs of the stars, and the signs of the moon and of the sun are all in the hand of the Lord. Why do I search (them) out? 18 If He desires, He causes it to rain, morning and evening; And if He desires, He withholds it, And all things are in his hand.’ 19 And he prayed that night and said, ‘My God, God Most High, Thou alone art my God, And Thee and Thy dominion have I chosen. And Thou hast created all things, And all things that are the work of thy hands. 20 Deliver me from the hands of evil spirits who have dominion over the thoughts of men’s hearts, And let them not lead me astray from Thee, my God. And stablish Thou me and my seed for ever That we go not astray from henceforth and for evermore.’
Note that he prays for deliverance from “evil spirits who have dominion over the thoughts of men’s hearts” (cf. Jas 1:13-15) and that he and his seed will not go astray (cf. Jas 5:19-20). Verbal parallels should be checked… David Instone-Brewer suggests that James is a homily on the life of Abraham (as transmitted in Jubilees). He does not mention the possibility of a connection here at James 5:17-18 via Jubilees 12. This should be explored.