A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
neh 13:1UPON THE READING OF THE LAW SEPARATION IS MADE FROM THE MIXED MULTITUDE. (Neh 13:1-9)
On that day--This was not immediately consequent on the dedication of the city wall and gates, but after Nehemiah's return from the Persian court to Jerusalem, his absence having extended over a considerable period. The transaction here described probably took place on one of the periodical occasions for the public readings of the law, when the people's attention was particularly directed to some violations of it which called for immediate correction. There is another instance afforded, in addition to those which have already fallen under our notice, of the great advantages resulting from the public and periodical reading of the divine law. It was an established provision for the religious instruction of the people, for diffusing a knowledge and a reverence for the sacred volume, as well as for removing those errors and corruptions which might, in the course of time, have crept in.
the Ammonite and the Moabite should not come into the congregation of God for ever--that is, not be incorporated into the Israelitish kingdom, nor united in marriage relations with that people (Deu 23:3-4). This appeal to the authority of the divine law led to a dissolution of all heathen alliances (Neh 9:2; Ezr 10:3).
neh 13:4before this--The practice of these mixed marriages, in open neglect or violation of the law, had become so common, that even the pontifical house, which ought to have set a better example, was polluted by such an impure mixture.
Eliashib the priest . . . was allied unto Tobiah--This person was the high priest (Neh 13:28; also Neh 3:1), who, by virtue of his dignified office, had the superintendence and control of the apartments attached to the temple. The laxity of his principles, as well as of his practice, is sufficiently apparent from his contracting a family connection with so notorious an enemy of Israel as Tobiah. But his obsequious attentions had carried him much farther; for to accommodate so important a person as Tobiah on his occasional visits to Jerusalem, Eliashib had provided him a splendid apartment in the temple. The introduction of so gross an impropriety can be accounted for in no other way than by supposing that in the absence of the priests and the cessation of the services, the temple was regarded as a common public building, which might, in the circumstances, be appropriated as a palatial residence.
neh 13:6But in all this was not I at Jerusalem--Eliashib (concluding that, as Nehemiah had departed from Jerusalem, and, on the expiry of his allotted term of absence, had resigned his government, he had gone not to return) began to use great liberties, and, there being none left whose authority or frown he dreaded, allowed himself to do things most unworthy of his sacred office, and which, though in unison with his own irreligious character, he would not have dared to attempt during the residence of the pious governor. Nehemiah resided twelve years as governor of Jerusalem, and having succeeded in repairing and refortifying the city, he at the end of that period returned to his duties in Shushan. How long [Nehemiah] remained there is not expressly said, but "after certain days," which is a Scripture phraseology for a year or a number of years, he obtained leave to resume the government of Jerusalem; to his deep mortification and regret, he found matters in the neglected and disorderly state here described. Such gross irregularities as were practised, such extraordinary corruptions as had crept in, evidently imply the lapse of a considerable time. Besides, they exhibit the character of Eliashib, the high priest, in a most unfavorable light; for while he ought, by his office, to have preserved the inviolable sanctity of the temple and its furniture, his influence had been directly exercised for evil; especially he had given permission and countenance to a most indecent outrage--the appropriation of the best apartments in the sacred building to a heathen governor, one of the worst and most determined enemies of the people and the worship of God. The very first reform Nehemiah on his second visit resolved upon, was the stopping of this gross profanation [by Eliashib]. The chamber which had been polluted by the residence of the idolatrous Ammonite was, after undergoing the process of ritual purification (Num 15:9), restored to its proper use--a storehouse for the sacred vessels.
neh 13:10NEHEMIAH REFORMS THE OFFICERS IN THE HOUSE OF GOD. (Neh 13:10-14)
And I perceived that the portions of the Levites had not been given them--The people, disgusted with the malversations of Eliashib, or the lax and irregular performance of the sacred rites, withheld the tithes, so that the ministers of religion were compelled for their livelihood to withdraw to their patrimonial possessions in the country. The temple services had ceased; all religious duties had fallen into neglect. The money put into the sacred treasury had been squandered in the entertainment of an Ammonite heathen, an open and contemptuous enemy of God and His people. The return of the governor put an end to these disgraceful and profane proceedings. He administered a sharp rebuke to those priests to whom the management of the temple and its services was committed, for the total neglect of their duties, and the violation of the solemn promises which they had made to him at his departure. He upbraided them with the serious charge of having not only withheld from men their dues, but of having robbed God, by neglecting the care of His house and service. And thus having roused them to a sense of duty and incited them to testify their godly sorrow for their criminal negligence by renewed devotedness to their sacred work, Nehemiah restored the temple services. He recalled the dispersed Levites to the regular discharge of their duties; while the people at large, perceiving that their contributions would be no longer perverted to improper uses, willingly brought in their tithes as formerly. Men of integrity and good report were appointed to act as trustees of the sacred treasures, and thus order, regularity, and active service were re-established in the temple.
neh 13:15THE VIOLATION OF THE SABBATH. (Neh. 13:15-31)
In those days saw I in Judah some treading wine-presses on the sabbath--The cessation of the temple services had been necessarily followed by a public profanation of the Sabbath, and this had gone so far that labor was carried on in the fields, and fish brought to the markets on the sacred day. Nehemiah took the decisive step of ordering the city gates to be shut, and not to be opened, till the Sabbath was past; and in order to ensure the faithful execution of this order, he stationed some of his own servants as guards, to prevent the introduction of any commodities on that day. On the merchants and various dealers finding admission denied them, they set up booths outside the walls, in hopes of still driving a traffic with the peasantry; but the governor threatened, if they continued, to adopt violent measures for their removal. For this purpose a body of Levites was stationed as sentinels at the gate, with discretionary powers to protect the sanctification of the Sabbath.
neh 13:24could not speak in the Jews' language, but according to the language of each people--a mongrel dialect imbibed from their mothers, together with foreign principles and habits.
neh 13:25cursed them--that is, pronounced on them an anathema which entailed excommunication.
smote . . . and plucked off their hair--To cut off the hair of offenders seems to be a punishment rather disgraceful than severe; yet it is supposed that pain was added to disgrace, and that they tore off the hair with violence as if they were plucking a bird alive.