Both συμπαθέω and μετριοπαθέω are translated ‘have compassion,' but there is a marked difference between the words. μετριοπθέω (from, μετριοπαθής, moderate in passions') occurs but once in the N. T., Heb. 5:2, referring to the Levitical priest, who "exercised forbearance" (the true meaning of the word: 'reasonably bear with' margin) on the ignorant and the erring, being himself clothed with infirmity. Hence if compassion 'is admissible, it is as on the ignorant and erring.
συμπαθέω, (from σύν, ‘with,' and πάσχω, ‘to suffer') is to have sympathy with others who are suffering. The blessed Lord, having been tempted in all points apart from sin, can sympathize, not with sin, but with the infirmities of the saints (‘have a fellow-feeling,' as Bengel expresses it), Heb. 4:15. Paul was able to say that the believing Hebrews sympathized with him in his bonds, chap. 10:34; and all are exhorted to be sympathizing (' have compassion' A. V., συμπαθής), full of brotherly love, &c. 1 Pet. 3:8. The thought of compassion, not sympathy, can be connected with God: Christ can sympathize because, having become man, He has passed through trials: He has a fellow-feeling.
Neither of the words occurs in the LXX Vat., but the Alex. codex has συμπαθής in Job 29:25. Job says ‘I sat chief, and dwelt as a king in the midst of warriors, as one comforting fellow-mourners:' he was as one with them.