They have dealt treacherously against the LORD: for they have begotten strange children: now shall a month devour them with their portions.
They have dealt treacherously against the Lord - as to the marriage-covenant between God and Israel (Jeremiah 3:20).
For they have begotten strange children - alluding to "children of whoredoms" (Hosea 1:2; Hosea 2:4). "Strange," or foreign, implies that their idolatry was imported from abroad (Henderson). Or rather, 'regarded by God as strangers, not His,' as being reared in idolatry. The case is desperate, when not only the existing, but also the rising generation is reared in apostasy.
Now shall a month devour them - a very brief respite of time shall elapse, and then punishment shall overtake them (Zechariah 11:8, "Three shepherds also I cut off in one month"). The allusion seems to be to money loans, which were by the month, not as with us by the year. You cannot put it off: the time of your destruction is immediately and suddenly coming on you; just as the debtor must meet the creditor's demand at the expiration of the month. The prediction is of the invasion of Tiglath-pileser, who carried. away Reuben, Gad, Naphtali, and the half tribe of Manasseh.
With their portions - i:e., possessions. Their resources and garrisons will not avail to save them. Henderson explains, from Isaiah 57:6, "portions" as their idols: the context favours this, "the Lord," the true "portion of his people," being in antithesis to "their portions," the idols (Jeremiah 10:16, "The portion of Jacob is not like them: for he is the former of all things The Lord of hosts is his name").