God has form and He is formless too. Further, He is beyond both form and formlessness

Sri Ramakrishna: Some say that God has form and is not formless. Thus they start quarrelling. A Vaishnava quarrels with a Vedantist.

"One can rightly speak of God only after one has seen Him. He who has seen God knows really and truly that God has form and that He is formless as well. He has many other aspects that cannot be described.

"Once some blind men chanced to come near an animal that someone told them was an elephant. They were asked what the elephant was like. The blind men began to feel its body. One of them said the elephant was like a pillar; he had touched only its leg. Another said it was like a winnowing-fan; he had touched only its ear. In this way the others, having touched its tail or belly, gave their different versions of the elephant. Just so, a man who has seen only one aspect of God limits God to that alone. It is his conviction that God cannot be anything else.

(To the goswami) "How can you say that the only truth about God is that He has form? It is undoubtedly true that God comes down to earth in a human form, as in the case of Krishna. And it is true as well that God reveals Himself to His devotees in various forms. But it, is also true that God is formless; He is the Indivisible Existence-Knowledge-Bliss Absolute. He has been described in the Vedas both as formless and as endowed with form. He is also described there both as attributeless and as endowed with attributes.

Do you know what I mean? Satchidananda is like an infinite ocean. Intense cold freezes the water into ice, which floats on the ocean in blocks or various forms. Likewise, through the cooling influence of bhakti, one sees forms of God in the Ocean of the Absolute. These forms are meant for the bhaktas, the lovers of God. But when the Sun of Knowledge rises, the ice melts; it becomes the same water it was before. Water above and water below, everywhere nothing but water. Therefore a prayer in the Bhagavata says: 'O Lord, Thou hast form, and Thou art also formless. Thou walkest before us, O Lord, in the shape of a man; again, Thou hast been described in the Vedas as beyond words and thought.' (Ref: BG 12.1-4)*

But you may say that for certain devotees God assumes eternal forms. There are places in the ocean where the ice doesn't melt at all. It assumes the form of quartz." 

Kedar: "It is said in the Bhagavata that Vyasa asked God's forgiveness for his three transgressions. He said: 'O Lord, Thou art formless, but I have thought of Thee in my meditation as endowed with form; Thou art beyond speech, but I have sung Thee hymns; Thou art the All-pervading Spirit, but I have made pilgrimages to sacred places. Be gracious, O Lord, and forgive these three transgressions of mine.'"

Sri Ramakrishna: "Yes, God has form and He is formless too. Further, He is beyond both form and formlessness. No one can limit Him."

Source: Gospel of Sri Ramakrishna

Bhagavad Gita on God with and without form:

BG 12.1 Arjuna said Those devotees who, ever steadfast, thus worship Thee and those also who worship the imperishable and the unmanifested which of them are better versed in Yoga? 

BG 12.2 The Blessed Lord said Those who meditate on Me by fixing their minds on Me with steadfast devotion (and) being endowed with supreme faith-they are considered to be the most perfect yogis according to Me. 

BG 12.3 Those, however, who meditate in every way on the Immutable, the Indefinable, the Unmanifest, which is all-pervading, incomprehensible, change-less, immovable and constant.- 

BG 12.4 By fully controlling all the organs and always being even-minded, they, engaged in the welfare of all beings, attain Me alone. 

Ref: https://www.gitasupersite.iitk.ac.in/