Translation analysis: This verse changes in different versions, and not knowing the Hebrew I cannot discern the more likely original. The “problem” appears to be in the meaning of “they please themselves in the children of strangers.”
From the New American Standard:
For Thou (O Lord), hast abandoned Thy people, the house of Jacob,
Because they are filled with influences from the east,
And they (hearken unto) soothsayers like the Philistines,
And they strike bargains with the children of foreigners.
From Avraham Gileadi:
For thou, O Lord, has forsaken thy people,
the house of Jacob, because,
like the Philistines,
they provide themselves with
mystics from the East
and are content with the infantile heathen.
(Gileadi, The Book of Isaiah. P. 99)
The translations agree that there is a problem with influences from the east, and that the Israelites take counsel from the soothsayers or mystics. It is the final verse that has the widest variation. It does appear that the more frequent appearance of “children of foreigners” is the more preferred reading.
Scriptural analysis: There are two important sins laid at the door of Israel, listening to soothsayers, and doing something with “the children of foreigners.” Both of these are part of the influences of the “East.”
The Lord is unhappy with Israel’s practice of consulting soothsayers because it is a false copy of the revelation of their God to a prophet. The soothsayers claim to be in touch with some element of the divine, and through that contact are able to predict the future. The human race has always been interested in the near and personal future, and this is precisely the domain of the soothsayers. However, the soothsayers are not in contact with the God of Israel, and they provide only an imitation of true communication from the divine. It is for this reason that it becomes such a grievous sin, Israel has found a substitute for their God, and there should be no other god, nor any other intermediary in the will of the divine.
The question of the children is more complex because the translations differ. Both Gileadi and the NAS appear to prefer commerce as the issue, but it is difficult to see how commerce violates so completely the will of God. It is more likely that the “children of foreigners” is a problem related very specifically to “children” of foreigners.
George Lamsa interprets the passage thus:
"The alien children were taken captive during the wars and some of them were brought up as members of the family. It was against the law to mix thus with pagan people. The Israelites tried to keep their race holy and pure, but, at times, owing to marriages with alien women and the adoption of children, this was impossible…The rearing of strange children was discouraged by the Mosaic law. During the wars they were permitted to spare some of the virgin females, but they were told to destroy all the males.
“Now therefore kill every male among the little ones, and kill every woman that hath known man by lying with him. But all the women children, that have not known a man by lying with him, keep alive for yourselves.” (Num. 31:17-18).
The Israelites were to remain a pure race. Marriages with women of other races were discouraged. They were prohibited from giving their daughters to the uncircumcised (Gen. 34:14). Even after the captivity they were not permitted to marry Gentile women (Ezra 9:1-2). (Lamsa, George. Old Testament Light. P. 619).
The commandments to racial purity appear to be much more important than any business interactions with foreigners, which do not carry such heavy prohibitions. Therefore, this seems to be the more likely meaning. The Lord is unhappy with the influences from the East, in this verse, the importation of soothsayers that counterfeit true revelation, and the importation of the ‘children of foreigners’ which dilute the purity of Israel as a people.