  We treat an unbalanced shifted convolution sum of Fourier coefficients of
cusp forms. As a consequence, we obtain an upper bound for correlation of three
Hecke eigenvalues of holomorphic cusp forms $\sum_{H\leq h\leq
2H}W\big(\frac{h}{H}\big)\sum_{X\leq n\leq
2X}\lambda_{1}(n-h)\lambda_{2}(n)\lambda_{3}(n+h)$, which is nontrivial
provided that $H\geq X^{2/3+\varepsilon}$. The result can be viewed as a
cuspidal analogue of a recent result of Blomer on triple correlations of
divisor functions.
