Are the funds derived from escalating-yield investment certificates lawful or unlawful, and what if they are disposed of?

Deals involving investment certificates issued by banks that do not adhere to Sharia principles are forbidden because they include riba (usury/interest) and maysir (gambling). It is obligatory to withdraw funds from them and repent to Allah. You are entitled only to the principal amount you paid, as Allah Almighty says: "And if you repent, you may have your principal – [thus] you do no wrong, nor are you wronged." As for the interest, it is not permissible for you to possess it; rather, it should be taken and spent on charitable causes and for the general welfare of Muslims.