The law which states that 'a variation in an electric field causes magnetic field', is

Modified ampere circuital law is, $\oint \overrightarrow{B}·\overrightarrow{dL}={\mu }_0\left(i_c+i_d\right)$

$i_d$is the displacement current that is, $i_d={\mathrm{\epsilon }}_0\frac{d{\varphi }_{\mathrm{E}}}{dt}$

$\Rightarrow \oint \overrightarrow{B}·\overrightarrow{dL}={\mu }_0\left(i_c+{\mathrm{\epsilon }}_0\frac{d{\varphi }_{\mathrm{E}}}{dt}\right)$

Thus, it is clear from the above expression that modified ampere's law states that a variation in an electric field causes magnetic field.