SB 4.8.56
labdhva dravyamayim arcam
ksity-ambv-adisu varcayet
abhrtatma munih santo
yata-van mita-vanya-bhuk
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
It is possible to worship a form of the Lord made of physical elements such as earth, water, pulp, wood and metal. In the forest one can make a form with no more than earth and water and worship Him according to the above principles. A devotee who has full control over his self should be very sober and peaceful and must be satisfied simply with eating whatever fruits and vegetables are available in the forest.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
It is essential for a devotee to worship the form of the Lord and not only meditate upon the form of the Lord within his mind with the chanting of the mantra given by the spiritual master. The worship of the form must be present. The impersonalist takes unnecessary trouble to meditate upon or worship something impersonal, and the path is very precarious. We are not advised to follow the impersonalist way of meditating on or worshiping the Lord. Dhruva Maharaja was advised to worship a form made of earth and water because in the jungle, if it is not possible to have a form made of metal, wood or stone, the best process is to take earth mixed with water and make a form of the Lord and worship Him. The devotee should not be anxious about cooking food; whatever is available in the forest or in the city among the fruit and vegetable groups should be offered to the Deity, and the devotee should be satisfied eating that. He should not be anxious to have very palatable dishes. Of course, wherever it is possible one should offer the Deities the best foodstuffs, prepared within the category of fruits and vegetables, cooked or uncooked. The important factor is that the devotee should be regulated (mita-bhuk); that is one of the good qualifications of a devotee. He should not hanker to satisfy the tongue with a particular kind of foodstuff. He should be satisfied to eat whatever prasada is available by the grace of the Lord.