A loyal friend is a powerful defense:
whoever finds one has indeed found a treasure.

[φίλος πιστὸς σκέπη κραταιά,
ὁ δὲ εὑρὼν αὐτὸν εὗρεν θησαυρόν.]

The Bible (The Old Testament) (14th - 2nd C BC) Judeo-Christian sacred scripture [Tanakh, Hebrew Bible], incl. the Apocrypha (Deuterocanonicals)

Book 22b. Sirach (Ecclesiasticus) 6:14 (Sir 6:14) [NJB (1985)]
    (Source)

More on the history and acceptance of this Apocryphal book here and here.

(Source (Greek)). Other translations:

A faithfull friend is a strong defence: and he that hath found such an one hath found a treasure.
[KJV (1611)]

A faithful friend is a strong defence: and he that hath found him, hath found a treasure.
[DRA (1899)]

A faithful friend is a sure shelter,
whoever finds one has found a rare treasure.
[tr. JB (1966)]

A loyal friend is like a safe shelter; find one, and you have found a treasure.
[GNT (1976)]

Trustworthy friends are a strong shelter;
whoever finds one
has found a treasure.
[tr. CEB (2011)]

Faithful friends are a sturdy shelter;
whoever finds one has found a treasure.
[tr. NRSV (2021 ed.)]

A faithful friend is a firm friend;
And he that findeth him hath found a treasure.
[tr. RJPS (2023 ed.)]