Heidegger's Bible Handbook: Hebrews: Occasion of the Epistle
6. The occasion of writing was furnished by the Hebrews’ infirmity and affliction, and also mistrust, under which Paul was laboring, as if he was setting himself in opposition to the law.
Saint Paul had a twofold occasion for the writing of this Epistle. The Hebrews supplied the first, namely, their infirmity, who, although they had given their names to Christ, only very reluctantly bid farewell to the Levitical law, ceremonies, and worship, with error also affected among many, as it is evident out of Hebrews 5:11, 12: and their affliction, which they endured from the Gentiles: and their blasphemies, which they endured to the full, as if they attributed more to some apostate Nazarene than to Moses himself: and, finally, their persecutions, which they were undergoing on account of the name of Christ, as it is gathered out of Hebrews 10:34. The second was depending on Paul himself. For, not only was he ablaze with a singular love and zeal for helping his kinsmen, but he was also clearing away a suspicion, into which he had been brought, as if he were too rigidly setting himself in opposition to the ceremonies of the Mosaic law, and too freely preaching Christian liberty.