Parashas Naso · Passuk 5:15
That man shall bring his wife to the priest. And he shall bring as an offering for her one-tenth of an ephah of barley flour. No oil shall be poured upon it and no frankincense shall be laid on it, for it is a grain offering of jealousy, a grain offering of remembrance that recalls wrongdoing.
Chabad.org — English translation + Rashi
Source: Sotah 14a.
English: “And the man shall bring his wife” — this teaches that the husband brings his wife to the kohen; even so the Sages said that two Torah scholars are assigned to him lest he cohabit with her on the way.
In context: The verse places the initiative on the husband; the Sages add procedural safeguards during the journey to the Temple.
Custom
Chazal require the husband’s initiative and add the escort of two scholars to protect the integrity of the ordeal.