1)
What did the Mesharesim do?
1.
Malbim: They sweep in front of it.
2)
What are "u'Lehazkir u'Lehodos u'Lehalel"?
1.
'Rashi': Lehazkir is to say "Mizmor l'David Lehazkir" (Tehilim 38:1); Lehodos is to say "Hodu la'Shem Kir'u vi'Shmo" (ibid. 105:1). Lehalel refers to the Psalms that begin with Hallelukah.
2.
Malbim: Lehazkir is to mention Hashem's past deeds. Lehodos is thanking for His benefits. Lehalel is telling His praise.
