Is a loan from a supplementary retirement fund, repaid with 4.56% interest and exempted from income tax by an amount exceeding the interest paid, considered an usurious loan?

Borrowing with interest (riba) is strictly forbidden. It is authentically narrated in a Hadith (definition): "Allah has cursed the one who consumes riba, the one who pays it, its two witnesses, and its scribe." And he said: "They are all equal (in sin)." It is not permissible to engage in an interest-based loan just because the borrower will be exempt from tax due to it. For whoever fears Allah, He will suffice him and provide for him from where he does not expect, as Allah the Almighty said: "And whoever fears Allah – He will make for him a way out, and will provide for him from where he does not expect," and He also said: "And whoever fears Allah – He will make for him ease in his matter."