Mishneh Torah — Positive Mitzvot מצוות עשה, Chapter 57
The full Hebrew text of Mishneh Torah, Positive Mitzvot, Chapter 57, with English translation by Maimonides (Rambam).
לעשות פסח שני, שנאמר: "בַּחֹדֶשׁ הַשֵּׁנִי בְּאַרְבָּעָה עָשָׂר" (במדבר ט, יא).
To offer the second Paschal sacrifice, as [Numbers 9:11] states: "In the second month, on the fourteenth of the month...."