If sannyasis (persons in the renounced order of life, who have left their homes for self-realization) do not engage themselves in the devotional service of the Lord but become attracted by philanthropic work, such as opening educational institutions, hospitals or even monasteries, churches or temples of demigods, they find only trouble from such engagements, not only in this life but in the next. Sannyasis who do not take advantage of this life to realize Krsna simply waste their time and energy in activities outside the jurisdiction of the renounced order. A devotee's attempt to engage his energies in such activities as constructing a Visnu temple, however, is never wasted. Such engagements are called krsnarthe akhila-cesta, variegated activities performed to please Krsna. A philanthropist's opening a school building and a devotee's constructing a temple are not on the same level. Although a philanthropist's opening an educational institution may be pious activity, it comes under the laws of karma, whereas constructing a temple for Visnu is devotional service.

From Krsna book, by Srila Prabhupada. Ch. 87: Prayers by the Personified Vedas.