It is narrated from Sayyiduna Abu Musa (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "A believer to another believer is like a wall, one part of which strengthens another," and he (peace and blessings be upon him) interlaced his fingers.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الغصب / 11511