Midrash su Salmi 48:9

R. Joshua b. Levi said: "One who walks on a road and has no companion, shall study the Torah; for it is said (Pr. 1, 9.) For a wreath of grace are they; if a man have a headache, let him study the Torah, for it is said (Ib. ib. ib.) Are they unto thy head; if a man have a sore throat, let him study the Torah, for it is said (Ib. ib. ib.) And necklaces for thy neck; if a man have stomach sickness, he shall study the Torah, for it is said (Ib. 3, 8.) It will he healthy to thy body, if a man is sick with rheumatism, he shall study the Torah, for it is said (Ib. ib. ib.) And marrow to thy bones; if a man is sick in all or any part of his body, he shall study the Torah, for it is said (Ib. 4, 23.) And to the whole body a healing." R. Juda, the son of R. Chiya, said: "Come and see how the nature of the Holy One, praised be He! differs from that of mortal man. The nature of mortal man is that if a man prescribes a remedy, it may benefit one and injure another; but the Holy One, praised be He! gave the Torah to all Israel, as a remedy for all, and for the whole body, as it is said (Ib. ib. ib.) And to the whole body a healing." R. Ami said: "What is meant by the passage (Ib. 22, 18.) For it is a pleasant thing if thou keep them within thy bosom, if they be altogether firmly seated upon thy lips, i.e., when are the words of the Torah a pleasant thing? If thou keepeth them within thy bosom. And when canst thou keep them in thy bosom? If they are firmly seated upon thy lips." R. Zeira said: "We know from the following: (Ib. 15, 23.) A man hath joy by the answer of his mouth; and how good is a word spoken at the proper time! i.e., when has a man joy? If his mouth is able to answer [a question]." R. Isaac said: "We deduce the above from the following (Deu. 30, 14.) But the word is very nigh unto thee, in thy mouth, and in thy heart, that thou mayest do it, i.e., when is the word nigh unto thee? If it is in thy mouth and in thy heart to do it." Raba said: "We deduce the above from the following (Ps. 21, 3.) The longing of his heart hast Thou given him and the request of his lips hast thou not withheld, Selah, i.e., when hast Thou given him the request of his heart? If the request was not withheld by his lips, Selah." Raba raised the following contradictory question: "It is written (Ib. ib. ib.) The longing of his heart hast Thou given him; [even without praying]; and immediately following, And the request of his lips hast Thou not withheld, Selah. And he answered thus: If the man has merited it, the longing of his heart is given him without requesting it; but if he has not merited it, he must first request it before it is granted to him." In the school of R. Eliezer b. Jacob it was taught: "Wherever we find Netzach, Selah, Va'ed, forming the conclusion of a passage, it signifies that it will be forever, without interruption." As for Netzach, it is written (Is. 57, 16.) For not to eternity will I contend, neither will I be wroth (Lanetzath) forever. As for Selah, it is written (Ps. 48, 9.) As we have heard, so have we seen, in the city of the Lord of Hosts, in the city of our God; God will establish it forever, Selah; as for Va'ed, it is written (Ex. 15, 18.) The Lord will reign forever, and ever (Va'ed) . R. Elazar said: "What is the meaning of the passage (Pr. 1, 9.) And necklace around thy neck, i.e., just as a necklace is loose around the neck and is not seen, all the time [as when the wearer is bending down, so is it with a man. If he is not constantly seen in the streets or markets, but sits at home and studies] he will retain his learning; but if otherwise, he will not retain his learning."