رسخ1 رَسَخَ, (S, A, L, &c.,) aor. ـَ (A, Msb, JM, &c.,) inf. n. رُسُوخٌ, It (a thing, S, Msb) was, or became, firm, steady, steadfast, stable, fixed, fast, settled, or established, (S, A, L, Msb, K,) in its place. (L.) [Hence,] رَسَخَ الحِبْرُ فِى الصَّحِيفَةِ (tropical:)  [The ink became fixed upon the piece of paper or the like]. (A, L.) And الرَّقُّ الدَّهِينُ لَا يُرْسَخُ فِيهِ الحِبْرُ (tropical:)  [Ink will not become fixed upon oiled parchment]: (A:) or الوَرَقُ الدَّهِينُ [oiled paper]. (TA.) And رَسَخَ فِى العِلْمِ (tropical:)  He became firmly rooted, or grounded, or established, in science, or knowledge. (L.) And العِلْمُ يَرْسَخُ فِى قَلْبِ الإِنْسَانِ (tropical:)  Science, or knowledge, becomes firmly rooted, or grounded, or fixed, in the heart of man. (L, A. *) And رَسَخَ حُبُّهُ فِى قَلْبِهِ (tropical:)  [The love of him, or it, became fixed in his heart]. (A.) b2:  [Hence also,] said of a pool of water left by a torrent, (tropical:)  It sank into the earth, and disappeared: (JK, A, K:) inf. n. as above. (JK, TA.) And, said of rain, (tropical:)  It sank into the earth so that the two moistures [meaning that of the rain and that of the soil beneath] met together. (A, K.) b3:  رَسْخٌ [as an inf. n.] signifies (assumed tropical:)  The connexion of the soul of a human being, after its departure from the body, with an inanimate, not increasing, body: distinguished  from نَسْخٌ, which is with the body of another human being: and from مَسْخٌ, which is with the body of a beast: and from فَسْخٌ, which is with a plant. (Marginal note in a copy of the KT.) But  see 1 (last sentence) in art. فسخ4 ارسخهُ, (JK, K,) inf. n. إِرْسَاخٌ, (TA,) He made it firm, steady, steadfast, stable, fixed, fast, settled, or established, (JK, K,) in its place. (JK.) رَاسِخٌ Anything firm, steady, steadfast, stable, fixed, fast, settled, or established [in its place (see 1)]. (S, A, Msb.) You say جَبَلٌ رَاسِخٌ A firm, or steadfast, mountain. (A.) And in like manner دِمْنَةٌ رَاسِخَةٌ [A black, or dark, patch of compacted dung and urine of cattle sticking fast upon the ground]. (A.) And [hence,] لَهُ قَدَمٌ رَاسِخَةٌ فِى العِلْمِ (assumed tropical:)  [He has a firm footing in science, or knowledge; or] he possesses excellence, and large acquirements, in science, or knowledge. (Msb.) الرَّاسِخُونَ فِى العِلْمِ [in the Kur iii. 5 and iv. 160] means (tropical:)  Those who are firmly rooted, or established, in science, or knowledge: (S, Bd, L, Jel, TA:) or who have made a firm advance therein: (L:) or who are far advanced therein: (Khálid Ibn-Jembeh:) or those who study the Book of God: (TA:) or those who have committed [it] to memory, and who call to mind [its doctrines and precepts] one with another. (IAar.)