L’Exode 23:14 Midrash : Sifrei Devarim

שָׁלֹ֣שׁ רְגָלִ֔ים תָּחֹ֥ג לִ֖י בַּשָּׁנָֽה׃

Trois fois l’an, tu célébreras des fêtes en mon honneur.

Sifrei Devarim

Which minor is exempt? One who cannot "ride" on his father's shoulder and go up to Jerusalem to the Temple mount. These are the words of Beth Shammai, it being written "your males." Beth Hillel say: One who cannot hold on to his father's hand and go up to Jerusalem to the Temple mount, it being written (Shemoth 23:14) "Three regalim (festivals)," lit., "feet."