Good night

The Talmud learns[1] from the verse which says, "From the shining of the sun until it comes [downs, i.e. sundown][2]" that Hallel is not supposed to be recited at night. Based on this, Rabbi Aryeh Leib Ginzburg (1700-1785) asked[3] why one is required to say Hallel on the first night of Passover if one is not supposed to recite Hallel at night. He answered that the Hallel recited on the night of Passover is not a requirement of its own; rather, it is a logical outcome of the fulfillment of the positive commandment of discussing the events of the Exodus on the night of Passover[4]. Similarly, according to the explanation of Rabbi Swerdloff, one can explain that the recitation of Hallel is part of the commandment of eating Matzoh. According to the Brisker Rov, one can answer that the "recitation" of Hallel is not supposed to be said at night, but the "song" type of Hallel, is allowed to be sung at night.

[1] Megillah 20b
[2] Psalms 113:3
[3] Turei Even to Megillah 15a
[4] Exodus 13:8