‘And I commanded the Levites that they should purify themselves, and that they should come and keep the gates, to sanctify the sabbath day.'
As a longer term measure Nehemiah called on the Levites, of whom many were experienced gatekeepers, to come and guard the gates. This was not in order to act in a military role, but so as to preserve the sanctity of the Sabbath, a fitting levitical duty. The religious aspect of their appointment is brought out in that they had to purify themselves. They were to have their part in preserving the holiness of Jerusalem without which God's future promises could not come to fruition, and in order fittingly to do this it was necessary for them to be purified. The use of Levites would have disarmed the population who may well otherwise have become uneasy at the role being carried out exclusively by Nehemiah's own men, and suggests that Nehemiah's position enjoyed some considerable support in the Temple. As in Nehemiah 13:1 the subsection then ends with a ‘remember --' request to God.
‘Remember with respect to me, O my God, this also, and spare me according to the greatness of your covenant love.'
His prayer here is that God will take note of what he has done in protecting the sanctity of His Sabbath day, and will thus spare him, not as a reward, but in view of the greatness of the covenant love revealed in that same covenant that he had protected.
It is noteworthy that Nehemiah only asks God to remember what he has done when it is in direct fulfilment of His covenant. (Thus he does not ask to be remembered for rebuilding the walls of Jerusalem). In Nehemiah 5:19 it was because he had ensured the carrying out of the provisions of the Law for the poor of the land (e.g. in Deuteronomy 15:1-11), and the Law against a ruler piling up wealth (Deuteronomy 17:17). In Nehemiah 13:14 it was because he had fulfilled the provisions of the Law by expelling an Ammonite from permanent residence in the Temple in accordance with Deuteronomy 23. Here it is because he has ensured the fulfilment of the fourth commandment (Exodus 20:8-10). In Nehemiah 13:31 it is because he has ensured the purity of the priesthood and of the Temple in accordance with the Law, has ensured that the God-chosen priests and Levites have fulfilled their legal responsibilities, has ensured sufficient supplies of wood for the sacrificial fires, and has ensured the gathering of the firstfruits, all in accordance with the Law.