In reply to sandeep1291:
You need to use local variable. Pseudo-code (Untested):
// Assuming default clk, disable
property p_check_a_b;
int v_a; // same datatype as a
(!$stable(a), v_a = a)|-> ##5 (v_a==b);
endproperty : p_check_a_b
a_p_check_a_b : assert property (p_check_a_b) else `uvm_error("failed");
HTH
Srini
www.verifworks.com