Boiling point is highest for

Strength of hydrogen bonding depends on the size and electronegativity of the atom.

Smaller the size of the atom, greater is the electronegativity and hence stronger is the $\mathrm{H}$-bonding. Thus, the order of strength of $\mathrm{H}$-bonding is $\mathrm{H}..\mathrm{F}>\mathrm{H}\dots \mathrm{O}>\mathrm{H}...\mathrm{N}$.

But each HF molecule is linked only to two other HF molecules while each H₂O molecule is linked to four other H₂O molecules through H-bonding.
Hence, the decreasing order of boiling points is ${\mathrm{H}}_2\mathrm{O}>\mathrm{HF}>{\mathrm{NH}}_3$.